Provide user with option to control how properties are generated.

src/Features/Core/Portable/ImplementInterface/AbstractImplementInterfaceService.CodeAction.cs

@@ -176,15 +176,15 @@ public Task<Document> GetUpdatedDocumentAsync(CancellationToken cancellationToke
                 var compilation = await result.Project.GetCompilationAsync(cancellationToken).ConfigureAwait(false);
 
                 var isComImport = unimplementedMembers.Any(t => t.Item1.IsComImport);
+                var options = await document.GetOptionsAsync(cancellationToken).ConfigureAwait(false);
+                var propertyGenerationBehavior = options.GetOption(ImplementTypeOptions.PropertyGenerationBehavior);
+
                 var memberDefinitions = GenerateMembers(
-                    compilation,
-                    unimplementedMembers,
-                    cancellationToken);
+                    compilation, unimplementedMembers, propertyGenerationBehavior, cancellationToken);
 
                 // Only group the members in the destination if the user wants that *and* 
                 // it's not a ComImport interface.  Member ordering in ComImport interfaces 
                 // matters, so we don't want to much with them.
-                var options = await document.GetOptionsAsync(cancellationToken).ConfigureAwait(false);
                 var insertionBehavior = options.GetOption(ImplementTypeOptions.InsertionBehavior);
                 var groupMembers = !isComImport &&
                     insertionBehavior == ImplementTypeInsertionBehavior.WithOtherMembersOfTheSameKind;
@@ -203,6 +203,7 @@ public Task<Document> GetUpdatedDocumentAsync(CancellationToken cancellationToke
             private ImmutableArray<ISymbol> GenerateMembers(
                 Compilation compilation,
                 ImmutableArray<(INamedTypeSymbol type, ImmutableArray<ISymbol> members)> unimplementedMembers,
+                ImplementTypePropertyGenerationBehavior propertyGenerationBehavior,
                 CancellationToken cancellationToken)
             {
                 // As we go along generating members we may end up with conflicts.  For example, say
@@ -229,7 +230,9 @@ public Task<Document> GetUpdatedDocumentAsync(CancellationToken cancellationToke
 
                     foreach (var unimplementedInterfaceMember in unimplementedInterfaceMembers)
                     {
-                        var member = GenerateMember(compilation, unimplementedInterfaceMember, implementedVisibleMembers, cancellationToken);
+                        var member = GenerateMember(
+                            compilation, unimplementedInterfaceMember, implementedVisibleMembers, 
+                            propertyGenerationBehavior, cancellationToken);
                         if (member != null)
                         {
                             implementedMembers.Add(member);
@@ -272,6 +275,7 @@ private string DetermineMemberName(ISymbol member, List<ISymbol> implementedVisi
                 Compilation compilation,
                 ISymbol member,
                 List<ISymbol> implementedVisibleMembers,
+                ImplementTypePropertyGenerationBehavior propertyGenerationBehavior,
                 CancellationToken cancellationToken)
             {
                 // First check if we already generate a member that matches the member we want to
@@ -308,7 +312,9 @@ private string DetermineMemberName(ISymbol member, List<ISymbol> implementedVisi
                 var syntaxFacts = Document.GetLanguageService<ISyntaxFactsService>();
                 var addUnsafe = member.IsUnsafe() && !syntaxFacts.IsUnsafeContext(State.Location);
 
-                return GenerateMember(compilation, member, memberName, generateInvisibleMember, generateAbstractly, addNew, addUnsafe, cancellationToken);
+                return GenerateMember(
+                    compilation, member, memberName, generateInvisibleMember, generateAbstractly,
+                    addNew, addUnsafe, propertyGenerationBehavior, cancellationToken);
             }
 
             private bool GenerateInvisibleMember(ISymbol member, string memberName)
@@ -376,6 +382,7 @@ private static bool IsUnexpressibleTypeParameter(ITypeParameterSymbol typeParame
                 bool generateAbstractly,
                 bool addNew,
                 bool addUnsafe,
+                ImplementTypePropertyGenerationBehavior propertyGenerationBehavior,
                 CancellationToken cancellationToken)
             {
                 var factory = this.Document.GetLanguageService<SyntaxGenerator>();
@@ -386,22 +393,16 @@ private static bool IsUnexpressibleTypeParameter(ITypeParameterSymbol typeParame
                     ? Accessibility.Public
                     : Accessibility.Private;
 
-                if (member.Kind == SymbolKind.Method)
+                if (member is IMethodSymbol method)
                 {
-                    var method = (IMethodSymbol)member;
-
                     return GenerateMethod(compilation, method, accessibility, modifiers, generateAbstractly, useExplicitInterfaceSymbol, memberName, cancellationToken);
                 }
-                else if (member.Kind == SymbolKind.Property)
+                else if (member is IPropertySymbol property)
                 {
-                    var property = (IPropertySymbol)member;
-
-                    return GenerateProperty(compilation, property, accessibility, modifiers, generateAbstractly, useExplicitInterfaceSymbol, memberName, cancellationToken);
+                    return GenerateProperty(compilation, property, accessibility, modifiers, generateAbstractly, useExplicitInterfaceSymbol, memberName, propertyGenerationBehavior, cancellationToken);
                 }
-                else if (member.Kind == SymbolKind.Event)
+                else if (member is IEventSymbol @event)
                 {
-                    var @event = (IEventSymbol)member;
-
                     var accessor = CodeGenerationSymbolFactory.CreateAccessorSymbol(
                         attributes: default(ImmutableArray<AttributeData>),
                         accessibility: Accessibility.NotApplicable,

src/Features/Core/Portable/ImplementInterface/AbstractImplementInterfaceService.CodeAction_Property.cs

@@ -7,6 +7,7 @@
 using System.Threading;
 using Microsoft.CodeAnalysis.CodeGeneration;
 using Microsoft.CodeAnalysis.Editing;
+using Microsoft.CodeAnalysis.ImplementType;
 using Microsoft.CodeAnalysis.LanguageServices;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Shared.Utilities;
@@ -25,16 +26,19 @@ internal partial class ImplementInterfaceCodeAction
                 bool generateAbstractly,
                 bool useExplicitInterfaceSymbol,
                 string memberName,
+                ImplementTypePropertyGenerationBehavior propertyGenerationBehavior,
                 CancellationToken cancellationToken)
             {
                 var factory = this.Document.GetLanguageService<SyntaxGenerator>();
                 var attributesToRemove = AttributesToRemove(compilation);
 
-                var getAccessor = GenerateGetAccessor(compilation, property, accessibility, generateAbstractly,
-                    useExplicitInterfaceSymbol, attributesToRemove, cancellationToken);
+                var getAccessor = GenerateGetAccessor(
+                    compilation, property, accessibility, generateAbstractly, useExplicitInterfaceSymbol,
+                    propertyGenerationBehavior, attributesToRemove, cancellationToken);
 
-                var setAccessor = GenerateSetAccessor(compilation, property, accessibility,
-                    generateAbstractly, useExplicitInterfaceSymbol, attributesToRemove, cancellationToken);
+                var setAccessor = GenerateSetAccessor(
+                    compilation, property, accessibility, generateAbstractly, useExplicitInterfaceSymbol,
+                    propertyGenerationBehavior, attributesToRemove, cancellationToken);
 
                 var syntaxFacts = Document.GetLanguageService<ISyntaxFactsService>();
                 var parameterNames = NameGenerator.EnsureUniqueness(
@@ -73,6 +77,7 @@ private INamedTypeSymbol[] AttributesToRemove(Compilation compilation)
                 Accessibility accessibility,
                 bool generateAbstractly,
                 bool useExplicitInterfaceSymbol,
+                ImplementTypePropertyGenerationBehavior propertyGenerationBehavior,
                 INamedTypeSymbol[] attributesToRemove,
                 CancellationToken cancellationToken)
             {
@@ -81,6 +86,12 @@ private INamedTypeSymbol[] AttributesToRemove(Compilation compilation)
                     return null;
                 }
 
+                if (property.GetMethod == null)
+                {
+                    // Can't have an auto-prop with just a setter.
+                    propertyGenerationBehavior = ImplementTypePropertyGenerationBehavior.PreferThrowingProperties;
+                }
+
                 var setMethod = property.SetMethod.RemoveInaccessibleAttributesAndAttributesOfTypes(
                      this.State.ClassOrStructType,
                      attributesToRemove);
@@ -90,7 +101,8 @@ private INamedTypeSymbol[] AttributesToRemove(Compilation compilation)
                     attributes: default(ImmutableArray<AttributeData>),
                     accessibility: accessibility,
                     explicitInterfaceSymbol: useExplicitInterfaceSymbol ? property.SetMethod : null,
-                    statements: GetSetAccessorStatements(compilation, property, generateAbstractly, cancellationToken));
+                    statements: GetSetAccessorStatements(
+                        compilation, property, generateAbstractly, propertyGenerationBehavior, cancellationToken));
             }
 
             private IMethodSymbol GenerateGetAccessor(
@@ -99,6 +111,7 @@ private INamedTypeSymbol[] AttributesToRemove(Compilation compilation)
                 Accessibility accessibility,
                 bool generateAbstractly,
                 bool useExplicitInterfaceSymbol,
+                ImplementTypePropertyGenerationBehavior propertyGenerationBehavior,
                 INamedTypeSymbol[] attributesToRemove,
                 CancellationToken cancellationToken)
             {
@@ -116,13 +129,15 @@ private INamedTypeSymbol[] AttributesToRemove(Compilation compilation)
                     attributes: default(ImmutableArray<AttributeData>),
                     accessibility: accessibility,
                     explicitInterfaceSymbol: useExplicitInterfaceSymbol ? property.GetMethod : null,
-                    statements: GetGetAccessorStatements(compilation, property, generateAbstractly, cancellationToken));
+                    statements: GetGetAccessorStatements(
+                        compilation, property, generateAbstractly, propertyGenerationBehavior, cancellationToken));
             }
 
             private ImmutableArray<SyntaxNode> GetSetAccessorStatements(
                 Compilation compilation,
                 IPropertySymbol property,
                 bool generateAbstractly,
+                ImplementTypePropertyGenerationBehavior propertyGenerationBehavior,
                 CancellationToken cancellationToken)
             {
                 if (generateAbstractly)
@@ -157,13 +172,16 @@ private INamedTypeSymbol[] AttributesToRemove(Compilation compilation)
                     return ImmutableArray.Create(factory.ExpressionStatement(expression));
                 }
 
-                return factory.CreateThrowNotImplementedStatementBlock(compilation);
+                return propertyGenerationBehavior == ImplementTypePropertyGenerationBehavior.PreferAutoProperties
+                    ? default(ImmutableArray<SyntaxNode>)
+                    : factory.CreateThrowNotImplementedStatementBlock(compilation);
             }
 
             private ImmutableArray<SyntaxNode> GetGetAccessorStatements(
                 Compilation compilation,
                 IPropertySymbol property,
                 bool generateAbstractly,
+                ImplementTypePropertyGenerationBehavior propertyGenerationBehavior,
                 CancellationToken cancellationToken)
             {
                 if (generateAbstractly)
@@ -196,8 +214,10 @@ private INamedTypeSymbol[] AttributesToRemove(Compilation compilation)
                     return ImmutableArray.Create(factory.ReturnStatement(expression));
                 }
 
-                return factory.CreateThrowNotImplementedStatementBlock(compilation);
+                return propertyGenerationBehavior == ImplementTypePropertyGenerationBehavior.PreferAutoProperties
+                    ? default(ImmutableArray<SyntaxNode>)
+                    : factory.CreateThrowNotImplementedStatementBlock(compilation);
             }
         }
     }
-}
+}
\ No newline at end of file

src/Features/Core/Portable/ImplementInterface/AbstractImplementInterfaceService.cs

 // 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 System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;

src/Features/Core/Portable/ImplementType/ImplementTypeOptions.cs

@@ -10,6 +10,12 @@ internal enum ImplementTypeInsertionBehavior
         AtTheEnd = 1,
     }
 
+    internal enum ImplementTypePropertyGenerationBehavior
+    {
+        PreferThrowingProperties = 0,
+        PreferAutoProperties = 1,
+    }
+
     internal static class ImplementTypeOptions
     {
         public static readonly PerLanguageOption<ImplementTypeInsertionBehavior> InsertionBehavior = 
@@ -19,5 +25,14 @@ internal static class ImplementTypeOptions
                 defaultValue: ImplementTypeInsertionBehavior.WithOtherMembersOfTheSameKind,
                 storageLocations: new RoamingProfileStorageLocation(
                     $"TextEditor.%LANGUAGE%.{nameof(ImplementTypeOptions)}.{nameof(InsertionBehavior)}"));
+
+        public static readonly PerLanguageOption<ImplementTypePropertyGenerationBehavior> PropertyGenerationBehavior =
+            new PerLanguageOption<ImplementTypePropertyGenerationBehavior>(
+                nameof(ImplementTypeOptions),
+                nameof(PropertyGenerationBehavior),
+                defaultValue: ImplementTypePropertyGenerationBehavior.PreferThrowingProperties,
+                storageLocations: new RoamingProfileStorageLocation(
+                    $"TextEditor.%LANGUAGE%.{nameof(ImplementTypeOptions)}.{nameof(PropertyGenerationBehavior)}"));
+
     }
 }
\ No newline at end of file

src/VisualStudio/CSharp/Impl/Options/AdvancedOptionPageControl.xaml

@@ -100,6 +100,16 @@
                                               x:Name="at_the_end"
                                               Content="{x:Static local:AdvancedOptionPageStrings.Option_at_the_end}"/>
                     </StackPanel>
+
+                    <Label Content="{x:Static local:AdvancedOptionPageStrings.Option_When_generating_properties}"/>
+                    <StackPanel Margin="15, 0, 0, 0">
+                        <RadioButton  GroupName="Property_generation_behavior"
+                                              x:Name="prefer_throwing_properties"
+                                              Content="{x:Static local:AdvancedOptionPageStrings.Option_prefer_throwing_properties}"/>
+                        <RadioButton  GroupName="Property_generation_behavior"
+                                              x:Name="prefer_auto_properties"
+                                              Content="{x:Static local:AdvancedOptionPageStrings.Option_prefer_auto_properties}"/>
+                    </StackPanel>
                 </StackPanel>
             </GroupBox>
         </StackPanel>

src/VisualStudio/CSharp/Impl/Options/AdvancedOptionPageControl.xaml.cs

@@ -48,6 +48,9 @@ public AdvancedOptionPageControl(IServiceProvider serviceProvider) : base(servic
 
             BindToOption(with_other_members_of_the_same_kind, ImplementTypeOptions.InsertionBehavior, ImplementTypeInsertionBehavior.WithOtherMembersOfTheSameKind, LanguageNames.CSharp);
             BindToOption(at_the_end, ImplementTypeOptions.InsertionBehavior, ImplementTypeInsertionBehavior.AtTheEnd, LanguageNames.CSharp);
+
+            BindToOption(prefer_throwing_properties, ImplementTypeOptions.PropertyGenerationBehavior, ImplementTypePropertyGenerationBehavior.PreferThrowingProperties, LanguageNames.CSharp);
+            BindToOption(prefer_auto_properties, ImplementTypeOptions.PropertyGenerationBehavior, ImplementTypePropertyGenerationBehavior.PreferAutoProperties, LanguageNames.CSharp);
         }
     }
 }
\ No newline at end of file

src/VisualStudio/CSharp/Impl/Options/AdvancedOptionPageStrings.cs

@@ -62,6 +62,15 @@ public static string Option_with_other_members_of_the_same_kind
         public static string Option_at_the_end
             => ServicesVSResources.at_the_end;
 
+        public static string Option_When_generating_properties
+            => ServicesVSResources.When_generating_properties;
+
+        public static string Option_prefer_auto_properties
+            => ServicesVSResources.prefer_auto_properties;
+
+        public static string Option_prefer_throwing_properties
+            => ServicesVSResources.prefer_throwing_properties;
+
         public static string Option_GenerateXmlDocCommentsForTripleSlash
         {
             get { return CSharpVSResources.Generate_XML_documentation_comments_for; }

src/VisualStudio/Core/Def/ServicesVSResources.Designer.cs

@@ -1448,6 +1448,15 @@ internal class ServicesVSResources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to prefer auto properties.
+        /// </summary>
+        internal static string prefer_auto_properties {
+            get {
+                return ResourceManager.GetString("prefer_auto_properties", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Prefer braces.
         /// </summary>
@@ -1538,6 +1547,15 @@ internal class ServicesVSResources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to prefer throwing properties.
+        /// </summary>
+        internal static string prefer_throwing_properties {
+            get {
+                return ResourceManager.GetString("prefer_throwing_properties", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Preference.
         /// </summary>
@@ -2155,7 +2173,7 @@ internal class ServicesVSResources {
         internal static string Unfortunately_a_process_used_by_Visual_Studio_has_encountered_an_unrecoverable_error_We_recommend_saving_your_work_and_then_closing_and_restarting_Visual_Studio {
             get {
                 return ResourceManager.GetString("Unfortunately_a_process_used_by_Visual_Studio_has_encountered_an_unrecoverable_er" +
-                        "ror_We_recommend_saving_your_work_and_then_closing_and_restarting_Visual Studio", resourceCulture);
+                        "ror_We_recommend_saving_your_work_and_then_closing_and_restarting_Visual_Studio", resourceCulture);
             }
         }
         
@@ -2323,6 +2341,15 @@ internal class ServicesVSResources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to When generating properties:.
+        /// </summary>
+        internal static string When_generating_properties {
+            get {
+                return ResourceManager.GetString("When_generating_properties", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to When inserting properties, events and methods, place them:.
         /// </summary>

src/VisualStudio/Core/Def/ServicesVSResources.resx

@@ -873,7 +873,7 @@ Additional information: {1}</value>
   <data name="Pick_members" xml:space="preserve">
     <value>Pick members</value>
   </data>
-  <data name="Unfortunately_a_process_used_by_Visual_Studio_has_encountered_an_unrecoverable_error_We_recommend_saving_your_work_and_then_closing_and_restarting_Visual Studio" xml:space="preserve">
+  <data name="Unfortunately_a_process_used_by_Visual_Studio_has_encountered_an_unrecoverable_error_We_recommend_saving_your_work_and_then_closing_and_restarting_Visual_Studio" xml:space="preserve">
     <value>Unfortunately, a process used by Visual Studio has encountered an unrecoverable error.  We recommend saving your work, and then closing and restarting Visual Studio.</value>
   </data>
   <data name="Add_a_symbol_specification" xml:space="preserve">
@@ -900,4 +900,13 @@ Additional information: {1}</value>
   <data name="VisualStudioWorkspace_TryApplyChanges_cannot_be_called_from_a_background_thread" xml:space="preserve">
     <value>VisualStudioWorkspace.TryApplyChanges cannot be called from a background thread.</value>
   </data>
+  <data name="prefer_auto_properties" xml:space="preserve">
+    <value>prefer auto properties</value>
+  </data>
+  <data name="prefer_throwing_properties" xml:space="preserve">
+    <value>prefer throwing properties</value>
+  </data>
+  <data name="When_generating_properties" xml:space="preserve">
+    <value>When generating properties:</value>
+  </data>
 </root>
\ No newline at end of file