diff --git a/src/EditorFeatures/CSharpTest/ChangeSignature/AddParameterTests.Delegates.cs b/src/EditorFeatures/CSharpTest/ChangeSignature/AddParameterTests.Delegates.cs
index 1b11bc5e8a32bdf6974b635e84c5869b43d13209..9c97cb90af3f2b6499a5af7a488f60fc6b1d8b7b 100644
--- a/src/EditorFeatures/CSharpTest/ChangeSignature/AddParameterTests.Delegates.cs
+++ b/src/EditorFeatures/CSharpTest/ChangeSignature/AddParameterTests.Delegates.cs
@@ -845,6 +845,53 @@ void B()
         C2<D2>.D d = new C2<D2>.D(M);
         d(12345);
     }
+}";
+            await TestChangeSignatureViaCommandAsync(LanguageNames.CSharp, markup, updatedSignature: updatedSignature, expectedUpdatedInvocationDocumentCode: expectedUpdatedCode);
+        }
+
+        [WpfFact, Trait(Traits.Feature, Traits.Features.ChangeSignature)]
+        public async Task TestAddParameter_Delegates_Relaxation_ParameterlessFunctionToFunction()
+        {
+            var markup = @"
+class C0
+{
+    delegate int $$MyFunc(int x, string y, bool z);
+
+    class C
+    {
+        public void M()
+        {
+            MyFunc f = Test();
+        }
+
+        private MyFunc Test()
+        {
+            return null;
+        }
+    }
+}";
+            var updatedSignature = new[] {
+                new AddedParameterOrExistingIndex(2),
+                new AddedParameterOrExistingIndex(new AddedParameter("int", "newIntegerParameter", "12345")),
+                new AddedParameterOrExistingIndex(1)
+            };
+            var expectedUpdatedCode = @"
+class C0
+{
+    delegate int MyFunc(bool z, int newIntegerParameter, string y);
+
+    class C
+    {
+        public void M()
+        {
+            MyFunc f = Test();
+        }
+
+        private MyFunc Test()
+        {
+            return null;
+        }
+    }
 }";
             await TestChangeSignatureViaCommandAsync(LanguageNames.CSharp, markup, updatedSignature: updatedSignature, expectedUpdatedInvocationDocumentCode: expectedUpdatedCode);
         }
diff --git a/src/Features/VisualBasic/Portable/ChangeSignature/VisualBasicChangeSignatureService.vb b/src/Features/VisualBasic/Portable/ChangeSignature/VisualBasicChangeSignatureService.vb
index f73ba06aa77582d5ebba3e5658cae9bcb639250e..ca6428b268f721bead0bc22ab1c9b7863da7f550 100644
--- a/src/Features/VisualBasic/Portable/ChangeSignature/VisualBasicChangeSignatureService.vb
+++ b/src/Features/VisualBasic/Portable/ChangeSignature/VisualBasicChangeSignatureService.vb
@@ -432,11 +432,18 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ChangeSignature
         End Function
 
         Private Function PermuteDeclaration(Of T As SyntaxNode)(
-                                                               list As SeparatedSyntaxList(Of T),
+                                                               parameterList As SeparatedSyntaxList(Of T),
                                                                updatedSignature As SignatureChange,
                                                                createNewParameterMethod As Func(Of AddedParameter, T)) As SeparatedSyntaxList(Of T)
             Dim originalParameterSymbols = updatedSignature.OriginalConfiguration.ToListOfParameters().Select(Function(p) p.Symbol).ToArray()
             Dim reorderedParameters = updatedSignature.UpdatedConfiguration.ToListOfParameters()
+            Dim numSeparatorsToSkip = originalParameterSymbols.Length - reorderedParameters.Count
+
+            ' The parameter list could be empty if dealing with delegates.
+            If parameterList.IsEmpty() Then
+                Return SyntaxFactory.SeparatedList(parameterList, GetSeparators(parameterList, numSeparatorsToSkip))
+            End If
+
             Dim numAddedParameters = 0
 
             Dim newParameters = New List(Of T)
@@ -444,18 +451,17 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ChangeSignature
                 Dim existingParam = TryCast(newParam, ExistingParameter)
                 If existingParam IsNot Nothing Then
                     Dim pos = originalParameterSymbols.IndexOf(existingParam.Symbol)
-                    Dim param = list(pos)
+                    Dim param = parameterList(pos)
                     newParameters.Add(param)
                 Else
                     ' Added parameter
-                    numAddedParameters = numAddedParameters + 1
+                    numAddedParameters += 1
                     Dim newParameter = createNewParameterMethod(DirectCast(newParam, AddedParameter))
                     newParameters.Add(newParameter)
                 End If
             Next
 
-            Dim numSeparatorsToSkip = originalParameterSymbols.Length - reorderedParameters.Count
-            Return SyntaxFactory.SeparatedList(newParameters, GetSeparators(list, numSeparatorsToSkip))
+            Return SyntaxFactory.SeparatedList(newParameters, GetSeparators(parameterList, numSeparatorsToSkip))
         End Function
 
         Private Shared Function CreateNewArgumentSyntax(addedParameter As AddedParameter) As ArgumentSyntax
diff --git a/src/VisualStudio/CSharp/Impl/ChangeSignature/CSharpChangeSignatureLanguageService.cs b/src/VisualStudio/CSharp/Impl/ChangeSignature/CSharpChangeSignatureLanguageService.cs
index 3d03705a40bd2d38085403a1f6b229461cc95e0c..669b0bedcad08b1cfdc01c39d8c8c93a0f1478d7 100644
--- a/src/VisualStudio/CSharp/Impl/ChangeSignature/CSharpChangeSignatureLanguageService.cs
+++ b/src/VisualStudio/CSharp/Impl/ChangeSignature/CSharpChangeSignatureLanguageService.cs
@@ -3,6 +3,8 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.VisualStudio.LanguageServices.Implementation.ChangeSignature;
 using Microsoft.VisualStudio.LanguageServices.Implementation.IntellisenseControls;
@@ -14,9 +16,9 @@
 namespace Microsoft.VisualStudio.LanguageServices.CSharp.ChangeSignature
 {
     [ExportLanguageService(typeof(IChangeSignatureLanguageService), LanguageNames.CSharp), Shared]
-    internal class CSharpChangeSignatureLanguageService : ChangeSignatureLanguageService, IChangeSignatureLanguageService
+    internal class CSharpChangeSignatureLanguageService : ChangeSignatureLanguageService
     {
-        public async Task<IntellisenseTextBoxViewModel[]> CreateViewModelsAsync(
+        public override async Task<IntellisenseTextBoxViewModel[]> CreateViewModelsAsync(
             string[] rolesCollectionType,
             string[] rolesCollectionName,
             int insertPosition,
@@ -42,11 +44,13 @@ ITrackingSpan[] CreateTrackingSpans(IProjectionSnapshot snapshot)
             }
         }
 
-        public void GeneratePreviewGrammar(AddedParameterViewModel addedParameterViewModel, List<SymbolDisplayPart> displayParts)
+        public override void GeneratePreviewGrammar(AddedParameterViewModel addedParameterViewModel, List<SymbolDisplayPart> displayParts)
         {
             displayParts.Add(new SymbolDisplayPart(SymbolDisplayPartKind.Keyword, null, addedParameterViewModel.Type));
             displayParts.Add(new SymbolDisplayPart(SymbolDisplayPartKind.Space, null, " "));
             displayParts.Add(new SymbolDisplayPart(SymbolDisplayPartKind.ParameterName, null, addedParameterViewModel.Parameter)); ;
         }
+
+        public override bool IsTypeNameValid(string typeName) => !SyntaxFactory.ParseTypeName(typeName).ContainsDiagnostics;
     }
 }
diff --git a/src/VisualStudio/Core/Def/Implementation/ChangeSignature/AbstractChangeSignatureLanguageService.cs b/src/VisualStudio/Core/Def/Implementation/ChangeSignature/AbstractChangeSignatureLanguageService.cs
index 9f145770db09f64cb09819bdbd7770d0aaa8ea9a..8a4782aae1279c73bc6e8d08d4b3e8d018d8f12b 100644
--- a/src/VisualStudio/Core/Def/Implementation/ChangeSignature/AbstractChangeSignatureLanguageService.cs
+++ b/src/VisualStudio/Core/Def/Implementation/ChangeSignature/AbstractChangeSignatureLanguageService.cs
@@ -2,6 +2,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.VisualStudio.LanguageServices.Implementation.IntellisenseControls;
 using Microsoft.VisualStudio.Text;
 using Microsoft.VisualStudio.Text.Projection;
@@ -22,6 +23,7 @@ internal abstract class AbstractChangeSignatureLanguageService : IChangeSignatur
             CancellationToken cancellationToken);
         public abstract void GeneratePreviewGrammar(ChangeSignatureDialogViewModel.AddedParameterViewModel addedParameterViewModel, List<SymbolDisplayPart> displayParts);
         public abstract IContentType GetContentType(IContentTypeRegistryService contentTypeRegistryService);
+        public abstract bool IsTypeNameValid(string typeName);
 
         protected ITrackingSpan[] CreateTrackingSpansHelper(IProjectionSnapshot snapshot, int contextPoint, int spaceBetweenTypeAndName)
         {
diff --git a/src/VisualStudio/Core/Def/Implementation/ChangeSignature/AddParameterDialog.xaml.cs b/src/VisualStudio/Core/Def/Implementation/ChangeSignature/AddParameterDialog.xaml.cs
index a68fb2bf9c8b3c6dc445956599df77246a8f25c7..2084e2510024e7d6b3f23a2060eb727215cf2597 100644
--- a/src/VisualStudio/Core/Def/Implementation/ChangeSignature/AddParameterDialog.xaml.cs
+++ b/src/VisualStudio/Core/Def/Implementation/ChangeSignature/AddParameterDialog.xaml.cs
@@ -5,6 +5,7 @@
 using Microsoft.VisualStudio.PlatformUI;
 using Microsoft.VisualStudio.Text.Editor;
 using Microsoft.VisualStudio.LanguageServices.Implementation.IntellisenseControls;
+using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Notification;
 
 namespace Microsoft.VisualStudio.LanguageServices.Implementation.ChangeSignature
@@ -17,6 +18,7 @@ internal partial class AddParameterDialog : DialogWindow
         public readonly AddParameterDialogViewModel ViewModel;
         private readonly IntellisenseTextBoxViewModel _typeIntellisenseTextBoxView;
         private readonly IntellisenseTextBoxViewModel _nameIntellisenseTextBoxView;
+        private readonly Document _document;
 
         public string OK { get { return ServicesVSResources.OK; } }
         public string Cancel { get { return ServicesVSResources.Cancel; } }
@@ -32,13 +34,15 @@ internal partial class AddParameterDialog : DialogWindow
         public AddParameterDialog(
             IntellisenseTextBoxViewModel typeIntellisenseTextBoxViewModel,
             IntellisenseTextBoxViewModel nameIntellisenseTextBoxViewModel,
-            INotificationService notificationService)
+            INotificationService notificationService,
+            Document document)
         {
             // The current implementation supports Add only.
             // The dialog should be initialized the other way if called for Edit.
             ViewModel = new AddParameterDialogViewModel(notificationService);
             _typeIntellisenseTextBoxView = typeIntellisenseTextBoxViewModel;
             _nameIntellisenseTextBoxView = nameIntellisenseTextBoxViewModel;
+            _document = document;
             this.Loaded += AddParameterDialog_Loaded;
             DataContext = ViewModel;
 
@@ -61,7 +65,7 @@ private void OK_Click(object sender, RoutedEventArgs e)
             ViewModel.TypeName = ((IntellisenseTextBox)TypeContentControl.Content).Text;
             ViewModel.ParameterName = ((IntellisenseTextBox)NameContentControl.Content).Text;
 
-            if (ViewModel.TrySubmit())
+            if (ViewModel.TrySubmit(_document))
             {
                 DialogResult = true;
             }
@@ -94,9 +98,11 @@ private void TypeNameContentControl_PreviewKeyDown(object sender, KeyEventArgs e
                     {
                         // Do nothing. This case is handled in parent control KeyDown events.
                     }
-                    else if (typeNameTextBox.ContainerName.Equals("NameContentControl") && e.Key == Key.Space)
+                    else if (e.Key == Key.Space &&
+                        (typeNameTextBox.ContainerName.Equals("NameContentControl") ||
+                        (typeNameTextBox.ContainerName.Equals("TypeContentControl") && _document.Project.Language.Equals(LanguageNames.CSharp))))
                     {
-                        // Do nothing. We disallow spaces in the name field for both C# and VB.
+                        // Do nothing. We disallow spaces in the name field for both C# and VB, and in the type field for C#.
                         e.Handled = true;
                     }
                     else
diff --git a/src/VisualStudio/Core/Def/Implementation/ChangeSignature/AddParameterDialogViewModel.cs b/src/VisualStudio/Core/Def/Implementation/ChangeSignature/AddParameterDialogViewModel.cs
index 08583fef5dead2d87b51bb4d7fddff38af90611f..f18652f361948147f41d2054c651bab8db35201b 100644
--- a/src/VisualStudio/Core/Def/Implementation/ChangeSignature/AddParameterDialogViewModel.cs
+++ b/src/VisualStudio/Core/Def/Implementation/ChangeSignature/AddParameterDialogViewModel.cs
@@ -1,6 +1,9 @@
 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.LanguageServices;
 using Microsoft.CodeAnalysis.Notification;
+using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.VisualStudio.LanguageServices.Implementation.Utilities;
 
 namespace Microsoft.VisualStudio.LanguageServices.Implementation.ChangeSignature
@@ -20,11 +23,23 @@ public AddParameterDialogViewModel(INotificationService notificationService)
 
         public string TypeName { get; set; }
 
-        internal bool TrySubmit()
+        internal bool TrySubmit(Document document)
         {
             if (string.IsNullOrEmpty(ParameterName) || string.IsNullOrEmpty(TypeName))
             {
-                SendFailureNotification("A type and name must be provided.");
+                SendFailureNotification(ServicesVSResources.A_type_and_name_must_be_provided);
+                return false;
+            }
+
+            if (!IsParameterTypeValid(TypeName, document))
+            {
+                SendFailureNotification(ServicesVSResources.Parameter_type_contains_invalid_characters);
+                return false;
+            }
+
+            if (!IsParameterNameValid(ParameterName, document))
+            {
+                SendFailureNotification(ServicesVSResources.Parameter_name_contains_invalid_characters);
                 return false;
             }
 
@@ -35,5 +50,17 @@ private void SendFailureNotification(string message)
         {
             _notificationService.SendNotification(message, severity: NotificationSeverity.Information);
         }
+
+        private bool IsParameterTypeValid(string typeName, Document document)
+        {
+            var languageService = document.GetLanguageService<IChangeSignatureLanguageService>();
+            return languageService.IsTypeNameValid(typeName);
+        }
+
+        private bool IsParameterNameValid(string identifierName, Document document)
+        {
+            var languageService = document.GetLanguageService<ISyntaxFactsService>();
+            return languageService.IsValidIdentifier(identifierName);
+        }
     }
 }
diff --git a/src/VisualStudio/Core/Def/Implementation/ChangeSignature/ChangeSignatureLanguageService.cs b/src/VisualStudio/Core/Def/Implementation/ChangeSignature/ChangeSignatureLanguageService.cs
index f305108667787351a99e9f0253ff4b32d70dd0b9..b02b919a7886dde28f3a0a95cc080d12fd533633 100644
--- a/src/VisualStudio/Core/Def/Implementation/ChangeSignature/ChangeSignatureLanguageService.cs
+++ b/src/VisualStudio/Core/Def/Implementation/ChangeSignature/ChangeSignatureLanguageService.cs
@@ -1,10 +1,20 @@
-using Microsoft.VisualStudio.Text;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+using Microsoft.VisualStudio.LanguageServices.Implementation.IntellisenseControls;
+using Microsoft.VisualStudio.Text;
 using Microsoft.VisualStudio.Text.Projection;
+using Microsoft.VisualStudio.Utilities;
 
 namespace Microsoft.VisualStudio.LanguageServices.Implementation.ChangeSignature
 {
-    internal class ChangeSignatureLanguageService
+    internal abstract class ChangeSignatureLanguageService : IChangeSignatureLanguageService
     {
+        public abstract Task<IntellisenseTextBoxViewModel[]> CreateViewModelsAsync(string[] rolesCollectionType, string[] rolesCollectionName, int insertPosition, Document document, string documentText, IContentType contentType, IntellisenseTextBoxViewModelFactory intellisenseTextBoxViewModelFactory, CancellationToken cancellationToken);
+        public abstract void GeneratePreviewGrammar(ChangeSignatureDialogViewModel.AddedParameterViewModel addedParameterViewModel, List<SymbolDisplayPart> displayParts);
+        public abstract bool IsTypeNameValid(string typeName);
+
         protected ITrackingSpan[] CreateTrackingSpansHelper(IProjectionSnapshot snapshot, int contextPoint, int spaceBetweenTypeAndName)
         {
             // Get the previous span/text.
diff --git a/src/VisualStudio/Core/Def/Implementation/ChangeSignature/IChangeSignatureLanguageService.cs b/src/VisualStudio/Core/Def/Implementation/ChangeSignature/IChangeSignatureLanguageService.cs
index 1b8641657502c9b4a5e43fe2c082cfd4f32c1e1a..3428dd9a76948a4dc4c2dc9406882703d91dbccc 100644
--- a/src/VisualStudio/Core/Def/Implementation/ChangeSignature/IChangeSignatureLanguageService.cs
+++ b/src/VisualStudio/Core/Def/Implementation/ChangeSignature/IChangeSignatureLanguageService.cs
@@ -4,6 +4,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Host;
 using Microsoft.VisualStudio.LanguageServices.Implementation.IntellisenseControls;
 using Microsoft.VisualStudio.Utilities;
@@ -24,5 +25,7 @@ internal interface IChangeSignatureLanguageService : ILanguageService
             CancellationToken cancellationToken);
 
         void GeneratePreviewGrammar(AddedParameterViewModel addedParameterViewModel, List<SymbolDisplayPart> displayParts);
+
+        bool IsTypeNameValid(string typeName);
     }
 }
diff --git a/src/VisualStudio/Core/Def/Implementation/ChangeSignature/VisualStudioChangeSignatureOptionsService.cs b/src/VisualStudio/Core/Def/Implementation/ChangeSignature/VisualStudioChangeSignatureOptionsService.cs
index 4b21b21be535f8c9bf5340e9acf8ba23f7fd2c31..f6a0350faeb3cfa03c44a6196ea0c6568e949181 100644
--- a/src/VisualStudio/Core/Def/Implementation/ChangeSignature/VisualStudioChangeSignatureOptionsService.cs
+++ b/src/VisualStudio/Core/Def/Implementation/ChangeSignature/VisualStudioChangeSignatureOptionsService.cs
@@ -115,7 +115,7 @@ public AddedParameterResult GetAddedParameter(Document document, int insertPosit
                 _intellisenseTextBoxViewModelFactory,
                 cancellationToken).ConfigureAwait(false);
 
-            return new AddParameterDialog(viewModels[0], viewModels[1], document.Project.Solution.Workspace.Services.GetService<INotificationService>());
+            return new AddParameterDialog(viewModels[0], viewModels[1], document.Project.Solution.Workspace.Services.GetService<INotificationService>(), document);
         }
     }
 }
diff --git a/src/VisualStudio/Core/Def/ServicesVSResources.Designer.cs b/src/VisualStudio/Core/Def/ServicesVSResources.Designer.cs
index 804b2db21990dd9eea4e23a5e1589b5c057c3944..61639eebd8cd22eb5cd9814a00fb87cd37d49774 100644
--- a/src/VisualStudio/Core/Def/ServicesVSResources.Designer.cs
+++ b/src/VisualStudio/Core/Def/ServicesVSResources.Designer.cs
@@ -144,6 +144,15 @@ internal class ServicesVSResources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to A type and name must be provided..
+        /// </summary>
+        internal static string A_type_and_name_must_be_provided {
+            get {
+                return ResourceManager.GetString("A_type_and_name_must_be_provided", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to _Access:.
         /// </summary>
@@ -2307,6 +2316,15 @@ internal class ServicesVSResources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Parameter name contains invalid character(s)..
+        /// </summary>
+        internal static string Parameter_name_contains_invalid_characters {
+            get {
+                return ResourceManager.GetString("Parameter_name_contains_invalid_characters", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Parameter preferences:.
         /// </summary>
@@ -2316,6 +2334,15 @@ internal class ServicesVSResources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Parameter type contains invalid character(s)..
+        /// </summary>
+        internal static string Parameter_type_contains_invalid_characters {
+            get {
+                return ResourceManager.GetString("Parameter_type_contains_invalid_characters", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Parameters:.
         /// </summary>
diff --git a/src/VisualStudio/Core/Def/ServicesVSResources.resx b/src/VisualStudio/Core/Def/ServicesVSResources.resx
index e8afdc5963e01ee151191d4e39e088d005c7864e..34fd7b1e0f9a5c5065b0350433f142af63aa1a9a 100644
--- a/src/VisualStudio/Core/Def/ServicesVSResources.resx
+++ b/src/VisualStudio/Core/Def/ServicesVSResources.resx
@@ -1064,9 +1064,15 @@ I agree to all of the foregoing:</value>
   <data name="Avoid_unused_value_assignments" xml:space="preserve">
     <value>Avoid unused value assignments</value>
   </data>
+  <data name="Parameter_name_contains_invalid_characters" xml:space="preserve">
+    <value>Parameter name contains invalid character(s).</value>
+  </data>
   <data name="Parameter_preferences_colon" xml:space="preserve">
     <value>Parameter preferences:</value>
   </data>
+  <data name="Parameter_type_contains_invalid_characters" xml:space="preserve">
+    <value>Parameter type contains invalid character(s).</value>
+  </data>
   <data name="Non_public_methods" xml:space="preserve">
     <value>Non-public methods</value>
   </data>
@@ -1178,6 +1184,9 @@ I agree to all of the foregoing:</value>
   <data name="A_new_namespace_will_be_created" xml:space="preserve">
     <value>A new namespace will be created</value>
   </data>
+  <data name="A_type_and_name_must_be_provided" xml:space="preserve">
+    <value>A type and name must be provided.</value>
+  </data>
   <data name="Rename_0_to_1" xml:space="preserve">
     <value>Rename {0} to {1}</value>
   </data>
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.cs.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.cs.xlf
index 6c18de0640052c5ed2d7253cb7da85b2a048710a..84313a87d2a3b6c2cdda82e323478bcbcbbd7098 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.cs.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.cs.xlf
@@ -12,6 +12,11 @@
         <target state="translated">Vytvoří se nový obor názvů.</target>
         <note />
       </trans-unit>
+      <trans-unit id="A_type_and_name_must_be_provided">
+        <source>A type and name must be provided.</source>
+        <target state="new">A type and name must be provided.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Add">
         <source>_Add</source>
         <target state="new">_Add</target>
@@ -437,11 +442,21 @@
         <target state="new">Parameter name:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_name_contains_invalid_characters">
+        <source>Parameter name contains invalid character(s).</source>
+        <target state="new">Parameter name contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parameter_preferences_colon">
         <source>Parameter preferences:</source>
         <target state="translated">Předvolby parametrů:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_type_contains_invalid_characters">
+        <source>Parameter type contains invalid character(s).</source>
+        <target state="new">Parameter type contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parentheses_preferences_colon">
         <source>Parentheses preferences:</source>
         <target state="translated">Předvolby závorek:</target>
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.de.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.de.xlf
index a1e9bde6bd4cc2f0b221e8e5f46fd7d5a2d75199..eb621b03000b840c21bb8bcef8cc10bc1d228183 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.de.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.de.xlf
@@ -12,6 +12,11 @@
         <target state="translated">Ein neuer Namespace wird erstellt.</target>
         <note />
       </trans-unit>
+      <trans-unit id="A_type_and_name_must_be_provided">
+        <source>A type and name must be provided.</source>
+        <target state="new">A type and name must be provided.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Add">
         <source>_Add</source>
         <target state="new">_Add</target>
@@ -437,11 +442,21 @@
         <target state="new">Parameter name:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_name_contains_invalid_characters">
+        <source>Parameter name contains invalid character(s).</source>
+        <target state="new">Parameter name contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parameter_preferences_colon">
         <source>Parameter preferences:</source>
         <target state="translated">Parametereinstellungen:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_type_contains_invalid_characters">
+        <source>Parameter type contains invalid character(s).</source>
+        <target state="new">Parameter type contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parentheses_preferences_colon">
         <source>Parentheses preferences:</source>
         <target state="translated">Voreinstellungen für Klammern:</target>
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.es.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.es.xlf
index af045ee04d9cdc90e0bd0bdaeafe674298fb23ff..66e8f7eb03cc2e924cbe940b8379cbb76e2882b2 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.es.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.es.xlf
@@ -12,6 +12,11 @@
         <target state="translated">Se creará un espacio de nombres</target>
         <note />
       </trans-unit>
+      <trans-unit id="A_type_and_name_must_be_provided">
+        <source>A type and name must be provided.</source>
+        <target state="new">A type and name must be provided.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Add">
         <source>_Add</source>
         <target state="new">_Add</target>
@@ -437,11 +442,21 @@
         <target state="new">Parameter name:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_name_contains_invalid_characters">
+        <source>Parameter name contains invalid character(s).</source>
+        <target state="new">Parameter name contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parameter_preferences_colon">
         <source>Parameter preferences:</source>
         <target state="translated">Preferencias de parámetros:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_type_contains_invalid_characters">
+        <source>Parameter type contains invalid character(s).</source>
+        <target state="new">Parameter type contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parentheses_preferences_colon">
         <source>Parentheses preferences:</source>
         <target state="translated">Preferencias de paréntesis:</target>
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.fr.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.fr.xlf
index 24e75c0ca20460da16559a7c9919ae17d72c86cb..8851944d2367fa10baebb0553455083322d7bad8 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.fr.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.fr.xlf
@@ -12,6 +12,11 @@
         <target state="translated">Un espace de noms va être créé</target>
         <note />
       </trans-unit>
+      <trans-unit id="A_type_and_name_must_be_provided">
+        <source>A type and name must be provided.</source>
+        <target state="new">A type and name must be provided.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Add">
         <source>_Add</source>
         <target state="new">_Add</target>
@@ -437,11 +442,21 @@
         <target state="new">Parameter name:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_name_contains_invalid_characters">
+        <source>Parameter name contains invalid character(s).</source>
+        <target state="new">Parameter name contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parameter_preferences_colon">
         <source>Parameter preferences:</source>
         <target state="translated">Préférences relatives aux paramètres :</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_type_contains_invalid_characters">
+        <source>Parameter type contains invalid character(s).</source>
+        <target state="new">Parameter type contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parentheses_preferences_colon">
         <source>Parentheses preferences:</source>
         <target state="translated">Préférences relatives aux parenthèses :</target>
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.it.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.it.xlf
index c1290b1089493dc4a4f1597b74d139122206b8d0..9666ce4ccdfe6c1a14fe35af249e0b40cf1d013b 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.it.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.it.xlf
@@ -12,6 +12,11 @@
         <target state="translated">Verrà creato un nuovo spazio dei nomi</target>
         <note />
       </trans-unit>
+      <trans-unit id="A_type_and_name_must_be_provided">
+        <source>A type and name must be provided.</source>
+        <target state="new">A type and name must be provided.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Add">
         <source>_Add</source>
         <target state="new">_Add</target>
@@ -437,11 +442,21 @@
         <target state="new">Parameter name:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_name_contains_invalid_characters">
+        <source>Parameter name contains invalid character(s).</source>
+        <target state="new">Parameter name contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parameter_preferences_colon">
         <source>Parameter preferences:</source>
         <target state="translated">Preferenze per parametri:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_type_contains_invalid_characters">
+        <source>Parameter type contains invalid character(s).</source>
+        <target state="new">Parameter type contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parentheses_preferences_colon">
         <source>Parentheses preferences:</source>
         <target state="translated">Preferenze per parentesi:</target>
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ja.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ja.xlf
index 88effc0cdc124484a1b0e362074c2af87b52a033..912862c56f35c4b4ec3ea2a55a20a45f318ee240 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ja.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ja.xlf
@@ -12,6 +12,11 @@
         <target state="translated">新しい名前空間が作成されます</target>
         <note />
       </trans-unit>
+      <trans-unit id="A_type_and_name_must_be_provided">
+        <source>A type and name must be provided.</source>
+        <target state="new">A type and name must be provided.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Add">
         <source>_Add</source>
         <target state="new">_Add</target>
@@ -437,11 +442,21 @@
         <target state="new">Parameter name:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_name_contains_invalid_characters">
+        <source>Parameter name contains invalid character(s).</source>
+        <target state="new">Parameter name contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parameter_preferences_colon">
         <source>Parameter preferences:</source>
         <target state="translated">パラメーターの優先順位:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_type_contains_invalid_characters">
+        <source>Parameter type contains invalid character(s).</source>
+        <target state="new">Parameter type contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parentheses_preferences_colon">
         <source>Parentheses preferences:</source>
         <target state="translated">かっこの優先順位:</target>
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ko.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ko.xlf
index b7b569767b8a1fe707e82d5dc23c9a4e12c3f41d..748f7dce4c0fd6271a786ba5c241966557f4b687 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ko.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ko.xlf
@@ -12,6 +12,11 @@
         <target state="translated">새 네임스페이스가 만들어집니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="A_type_and_name_must_be_provided">
+        <source>A type and name must be provided.</source>
+        <target state="new">A type and name must be provided.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Add">
         <source>_Add</source>
         <target state="new">_Add</target>
@@ -437,11 +442,21 @@
         <target state="new">Parameter name:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_name_contains_invalid_characters">
+        <source>Parameter name contains invalid character(s).</source>
+        <target state="new">Parameter name contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parameter_preferences_colon">
         <source>Parameter preferences:</source>
         <target state="translated">매개 변수 기본 설정:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_type_contains_invalid_characters">
+        <source>Parameter type contains invalid character(s).</source>
+        <target state="new">Parameter type contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parentheses_preferences_colon">
         <source>Parentheses preferences:</source>
         <target state="translated">괄호 기본 설정:</target>
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pl.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pl.xlf
index c8c9a47b363a5a2ed11f3d576f1667f63f5ccd64..a298d68970daade83dc927844938dcf6a48bd026 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pl.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pl.xlf
@@ -12,6 +12,11 @@
         <target state="translated">Zostanie utworzona nowa przestrzeń nazw</target>
         <note />
       </trans-unit>
+      <trans-unit id="A_type_and_name_must_be_provided">
+        <source>A type and name must be provided.</source>
+        <target state="new">A type and name must be provided.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Add">
         <source>_Add</source>
         <target state="new">_Add</target>
@@ -437,11 +442,21 @@
         <target state="new">Parameter name:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_name_contains_invalid_characters">
+        <source>Parameter name contains invalid character(s).</source>
+        <target state="new">Parameter name contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parameter_preferences_colon">
         <source>Parameter preferences:</source>
         <target state="translated">Preferencje dotyczące parametrów:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_type_contains_invalid_characters">
+        <source>Parameter type contains invalid character(s).</source>
+        <target state="new">Parameter type contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parentheses_preferences_colon">
         <source>Parentheses preferences:</source>
         <target state="translated">Preferencje dotyczące nawiasów:</target>
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pt-BR.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pt-BR.xlf
index 6ddfc81d95c5f67c95fba49de16f3f382b0cc8a4..437a97ca0fd9616812303b84a2994ebcfbfdcad9 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pt-BR.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pt-BR.xlf
@@ -12,6 +12,11 @@
         <target state="translated">Um namespace será criado</target>
         <note />
       </trans-unit>
+      <trans-unit id="A_type_and_name_must_be_provided">
+        <source>A type and name must be provided.</source>
+        <target state="new">A type and name must be provided.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Add">
         <source>_Add</source>
         <target state="new">_Add</target>
@@ -437,11 +442,21 @@
         <target state="new">Parameter name:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_name_contains_invalid_characters">
+        <source>Parameter name contains invalid character(s).</source>
+        <target state="new">Parameter name contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parameter_preferences_colon">
         <source>Parameter preferences:</source>
         <target state="translated">Preferências de parâmetro:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_type_contains_invalid_characters">
+        <source>Parameter type contains invalid character(s).</source>
+        <target state="new">Parameter type contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parentheses_preferences_colon">
         <source>Parentheses preferences:</source>
         <target state="translated">Preferências de parênteses:</target>
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ru.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ru.xlf
index b26945852fe12b82f32b3a2980e6a5bd4a9716a3..05a7736279e23f0870bdd37c3eb97dd4f2ed5884 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ru.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ru.xlf
@@ -12,6 +12,11 @@
         <target state="translated">Будет создано пространство имен</target>
         <note />
       </trans-unit>
+      <trans-unit id="A_type_and_name_must_be_provided">
+        <source>A type and name must be provided.</source>
+        <target state="new">A type and name must be provided.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Add">
         <source>_Add</source>
         <target state="new">_Add</target>
@@ -437,11 +442,21 @@
         <target state="new">Parameter name:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_name_contains_invalid_characters">
+        <source>Parameter name contains invalid character(s).</source>
+        <target state="new">Parameter name contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parameter_preferences_colon">
         <source>Parameter preferences:</source>
         <target state="translated">Предпочтения для параметров:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_type_contains_invalid_characters">
+        <source>Parameter type contains invalid character(s).</source>
+        <target state="new">Parameter type contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parentheses_preferences_colon">
         <source>Parentheses preferences:</source>
         <target state="translated">Параметры круглых скобок:</target>
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.tr.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.tr.xlf
index 82c6e26ea95377fc6c7c72726144a17a31db33dc..3f48603b6b7e8a494a174aeb1b3100de35118f9f 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.tr.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.tr.xlf
@@ -12,6 +12,11 @@
         <target state="translated">Yeni bir ad alanı oluşturulacak</target>
         <note />
       </trans-unit>
+      <trans-unit id="A_type_and_name_must_be_provided">
+        <source>A type and name must be provided.</source>
+        <target state="new">A type and name must be provided.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Add">
         <source>_Add</source>
         <target state="new">_Add</target>
@@ -437,11 +442,21 @@
         <target state="new">Parameter name:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_name_contains_invalid_characters">
+        <source>Parameter name contains invalid character(s).</source>
+        <target state="new">Parameter name contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parameter_preferences_colon">
         <source>Parameter preferences:</source>
         <target state="translated">Parametre tercihleri:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_type_contains_invalid_characters">
+        <source>Parameter type contains invalid character(s).</source>
+        <target state="new">Parameter type contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parentheses_preferences_colon">
         <source>Parentheses preferences:</source>
         <target state="translated">Parantez tercihleri:</target>
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hans.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hans.xlf
index e2ef5a4f7d8ab7e1cacca99b816be6243b019923..5097221ef357539f7c1a88fc3a4305d4cfdca326 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hans.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hans.xlf
@@ -12,6 +12,11 @@
         <target state="translated">将创建一个新的命名空间</target>
         <note />
       </trans-unit>
+      <trans-unit id="A_type_and_name_must_be_provided">
+        <source>A type and name must be provided.</source>
+        <target state="new">A type and name must be provided.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Add">
         <source>_Add</source>
         <target state="new">_Add</target>
@@ -437,11 +442,21 @@
         <target state="new">Parameter name:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_name_contains_invalid_characters">
+        <source>Parameter name contains invalid character(s).</source>
+        <target state="new">Parameter name contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parameter_preferences_colon">
         <source>Parameter preferences:</source>
         <target state="translated">参数首选项:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_type_contains_invalid_characters">
+        <source>Parameter type contains invalid character(s).</source>
+        <target state="new">Parameter type contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parentheses_preferences_colon">
         <source>Parentheses preferences:</source>
         <target state="translated">括号首选项:</target>
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hant.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hant.xlf
index ffda1c78f5cb329fbca1bf62d929a35e52f6d6c9..3b29f5cb04a618ea751a767ded3354e066b88979 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hant.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hant.xlf
@@ -12,6 +12,11 @@
         <target state="translated">將會建立新的命名空間</target>
         <note />
       </trans-unit>
+      <trans-unit id="A_type_and_name_must_be_provided">
+        <source>A type and name must be provided.</source>
+        <target state="new">A type and name must be provided.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Add">
         <source>_Add</source>
         <target state="new">_Add</target>
@@ -437,11 +442,21 @@
         <target state="new">Parameter name:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_name_contains_invalid_characters">
+        <source>Parameter name contains invalid character(s).</source>
+        <target state="new">Parameter name contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parameter_preferences_colon">
         <source>Parameter preferences:</source>
         <target state="translated">參數喜好設定:</target>
         <note />
       </trans-unit>
+      <trans-unit id="Parameter_type_contains_invalid_characters">
+        <source>Parameter type contains invalid character(s).</source>
+        <target state="new">Parameter type contains invalid character(s).</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Parentheses_preferences_colon">
         <source>Parentheses preferences:</source>
         <target state="translated">括號喜好設定:</target>
diff --git a/src/VisualStudio/VisualBasic/Impl/ChangeSignature/VisualBasicChangeSignatureLanguageService.vb b/src/VisualStudio/VisualBasic/Impl/ChangeSignature/VisualBasicChangeSignatureLanguageService.vb
index 1e7cdcf799aa66b4b2e4237f624dbefb4979a80a..24387084b904abf67758c510fca40442bf3e2c0e 100644
--- a/src/VisualStudio/VisualBasic/Impl/ChangeSignature/VisualBasicChangeSignatureLanguageService.vb
+++ b/src/VisualStudio/VisualBasic/Impl/ChangeSignature/VisualBasicChangeSignatureLanguageService.vb
@@ -3,7 +3,9 @@
 Imports System.Composition
 Imports System.Threading
 Imports Microsoft.CodeAnalysis
+Imports Microsoft.CodeAnalysis.CSharp.Syntax
 Imports Microsoft.CodeAnalysis.Host.Mef
+Imports Microsoft.CodeAnalysis.VisualBasic
 Imports Microsoft.VisualStudio.LanguageServices.Implementation.ChangeSignature
 Imports Microsoft.VisualStudio.LanguageServices.Implementation.IntellisenseControls
 Imports Microsoft.VisualStudio.Text
@@ -14,13 +16,12 @@ Namespace Microsoft.VisualStudio.LanguageServices.VisualBasic.ChangeSignature
     <ExportLanguageService(GetType(IChangeSignatureLanguageService), LanguageNames.VisualBasic), [Shared]>
     Friend Class VisualBasicChangeSignatureLanguageService
         Inherits ChangeSignatureLanguageService
-        Implements IChangeSignatureLanguageService
-        Public Async Function CreateViewModelsAsync(rolesCollectionType() As String,
+        Public Overrides Async Function CreateViewModelsAsync(rolesCollectionType() As String,
                                               rolesCollectionName() As String,
                                               insertPosition As Integer, document As Document,
                                               documentText As String, contentType As IContentType,
                                               intellisenseTextBoxViewModelFactory As IntellisenseTextBoxViewModelFactory,
-                                              cancellationToken As CancellationToken) As Task(Of IntellisenseTextBoxViewModel()) Implements IChangeSignatureLanguageService.CreateViewModelsAsync
+                                              cancellationToken As CancellationToken) As Task(Of IntellisenseTextBoxViewModel())
             Dim rolesCollections = {rolesCollectionName, rolesCollectionType}
 
             ' We insert '[]' so that we're always able to generate the type even if the name field is empty. 
@@ -38,9 +39,13 @@ Namespace Microsoft.VisualStudio.LanguageServices.VisualBasic.ChangeSignature
                 cancellationToken).ConfigureAwait(False)
         End Function
 
-        Public Sub GeneratePreviewGrammar(addedParameterViewModel As ChangeSignatureDialogViewModel.AddedParameterViewModel, displayParts As List(Of SymbolDisplayPart)) Implements IChangeSignatureLanguageService.GeneratePreviewGrammar
+        Public Overrides Sub GeneratePreviewGrammar(addedParameterViewModel As ChangeSignatureDialogViewModel.AddedParameterViewModel, displayParts As List(Of SymbolDisplayPart))
             displayParts.Add(New SymbolDisplayPart(SymbolDisplayPartKind.ParameterName, Nothing, addedParameterViewModel.Parameter))
             displayParts.Add(New SymbolDisplayPart(SymbolDisplayPartKind.Keyword, Nothing, " As " + addedParameterViewModel.Type))
         End Sub
+
+        Public Overrides Function IsTypeNameValid(typeName As String) As Boolean
+            Return Not SyntaxFactory.ParseTypeName(typeName).ContainsDiagnostics
+        End Function
     End Class
 End Namespace