use pattern matching

src/VisualStudio/CSharp/Impl/CodeModel/CSharpCodeModelService.cs

@@ -1406,8 +1406,7 @@ public override SyntaxNode SetDocComment(SyntaxNode node, string value)
                 throw Exceptions.ThrowEInvalidArg();
             }
 
-            var docElement = xmlDocument.FirstNode as XElement;
-            if (docElement == null ||
+            if (!(xmlDocument.FirstNode is XElement docElement) ||
                 docElement.Name.ToString().ToLower() != "doc")
             {
                 throw Exceptions.ThrowEInvalidArg();
@@ -1900,9 +1899,7 @@ public override EnvDTE80.vsCMParameterKind GetParameterKind(SyntaxNode node)
 
         public override SyntaxNode SetParameterKind(SyntaxNode node, EnvDTE80.vsCMParameterKind kind)
         {
-            var parameter = node as ParameterSyntax;
-
-            if (parameter == null)
+            if (!(node is ParameterSyntax parameter))
             {
                 throw Exceptions.ThrowEFail();
             }
@@ -2013,8 +2010,7 @@ public override bool GetCanOverride(SyntaxNode memberNode)
         {
             Debug.Assert(memberNode is MemberDeclarationSyntax);
 
-            var member = memberNode as MemberDeclarationSyntax;
-            if (member == null)
+            if (!(memberNode is MemberDeclarationSyntax member))
             {
                 throw Exceptions.ThrowEFail();
             }
@@ -2252,8 +2248,7 @@ public override bool GetMustImplement(SyntaxNode memberNode)
         {
             Debug.Assert(memberNode is MemberDeclarationSyntax);
 
-            var member = memberNode as MemberDeclarationSyntax;
-            if (member == null)
+            if (!(memberNode is MemberDeclarationSyntax member))
             {
                 throw Exceptions.ThrowEFail();
             }
@@ -2274,8 +2269,7 @@ public override SyntaxNode SetMustImplement(SyntaxNode memberNode, bool value)
                          memberNode is BasePropertyDeclarationSyntax ||
                          memberNode is EventFieldDeclarationSyntax);
 
-            var member = memberNode as MemberDeclarationSyntax;
-            if (member == null)
+            if (!(memberNode is MemberDeclarationSyntax member))
             {
                 throw Exceptions.ThrowEFail();
             }
@@ -2390,8 +2384,7 @@ public override SyntaxNode SetInheritanceKind(SyntaxNode typeNode, EnvDTE80.vsCM
         {
             Debug.Assert(typeNode is ClassDeclarationSyntax);
 
-            var member = typeNode as MemberDeclarationSyntax;
-            if (member == null)
+            if (!(typeNode is MemberDeclarationSyntax member))
             {
                 throw Exceptions.ThrowEFail();
             }
@@ -2532,8 +2525,7 @@ public override SyntaxNode SetIsAbstract(SyntaxNode memberNode, bool value)
         {
             Debug.Assert(memberNode is MemberDeclarationSyntax);
 
-            var member = memberNode as MemberDeclarationSyntax;
-            if (member == null)
+            if (!(memberNode is MemberDeclarationSyntax member))
             {
                 throw Exceptions.ThrowEFail();
             }
@@ -2562,8 +2554,7 @@ public override bool GetIsConstant(SyntaxNode variableNode)
                 return true;
             }
 
-            var member = GetNodeWithModifiers(variableNode) as MemberDeclarationSyntax;
-            if (member == null)
+            if (!(GetNodeWithModifiers(variableNode) is MemberDeclarationSyntax member))
             {
                 throw Exceptions.ThrowEFail();
             }
@@ -2586,8 +2577,7 @@ public override SyntaxNode SetIsConstant(SyntaxNode variableNode, bool value)
                 return variableNode;
             }
 
-            var member = variableNode as MemberDeclarationSyntax;
-            if (member == null)
+            if (!(variableNode is MemberDeclarationSyntax member))
             {
                 throw Exceptions.ThrowEFail();
             }
@@ -2615,8 +2605,7 @@ public override bool GetIsDefault(SyntaxNode propertyNode)
         {
             Debug.Assert(propertyNode is BasePropertyDeclarationSyntax);
 
-            var property = propertyNode as BasePropertyDeclarationSyntax;
-            if (property == null)
+            if (!(propertyNode is BasePropertyDeclarationSyntax property))
             {
                 throw Exceptions.ThrowEFail();
             }
@@ -2634,8 +2623,7 @@ public override bool GetIsGeneric(SyntaxNode memberNode)
         {
             Debug.Assert(memberNode is MemberDeclarationSyntax);
 
-            var member = GetNodeWithModifiers(memberNode) as MemberDeclarationSyntax;
-            if (member == null)
+            if (!(GetNodeWithModifiers(memberNode) is MemberDeclarationSyntax member))
             {
                 throw Exceptions.ThrowEFail();
             }
@@ -2656,8 +2644,7 @@ public override bool GetIsShared(SyntaxNode memberNode, ISymbol symbol)
             Debug.Assert(memberNode is MemberDeclarationSyntax ||
                          memberNode is VariableDeclaratorSyntax);
 
-            var member = GetNodeWithModifiers(memberNode) as MemberDeclarationSyntax;
-            if (member == null)
+            if (!(GetNodeWithModifiers(memberNode) is MemberDeclarationSyntax member))
             {
                 throw Exceptions.ThrowEFail();
             }
@@ -2669,8 +2656,7 @@ public override SyntaxNode SetIsShared(SyntaxNode memberNode, bool value)
         {
             Debug.Assert(memberNode is MemberDeclarationSyntax);
 
-            var member = memberNode as MemberDeclarationSyntax;
-            if (member == null)
+            if (!(memberNode is MemberDeclarationSyntax member))
             {
                 throw Exceptions.ThrowEFail();
             }
@@ -3715,11 +3701,9 @@ public override object GetTypeExtender(string name, AbstractCodeType symbol)
 
         protected override bool AddBlankLineToMethodBody(SyntaxNode node, SyntaxNode newNode)
         {
-            var newMethodDeclaration = newNode as MethodDeclarationSyntax;
-
             return node is MethodDeclarationSyntax methodDeclaration
                 && methodDeclaration.Body == null
-                && newMethodDeclaration != null
+                && newNode is MethodDeclarationSyntax newMethodDeclaration
                 && newMethodDeclaration.Body != null;
         }
 

src/VisualStudio/CSharp/Impl/EventHookup/EventHookupSessionManager_EventHookupSession.cs

@@ -191,8 +191,7 @@ private async Task<string> DetermineIfEventHookupAndGetHandlerNameAsync(Document
             private IEventSymbol GetEventSymbol(SemanticModel semanticModel, SyntaxToken plusEqualsToken, CancellationToken cancellationToken)
             {
                 AssertIsBackground();
-                var parentToken = plusEqualsToken.Parent as AssignmentExpressionSyntax;
-                if (parentToken == null)
+                if (!(plusEqualsToken.Parent is AssignmentExpressionSyntax parentToken))
                 {
                     return null;
                 }
@@ -254,7 +253,8 @@ private string GetNameObjectPart(IEventSymbol eventSymbol, SyntaxToken plusEqual
                 // Note: For generic, it's ok(it's even a good idea) to exclude type variables,
                 // because the name is only used as a prefix for the method name.
 
-                var typeDeclaration = syntaxFactsService.GetContainingTypeDeclaration(
+
+                return syntaxFactsService.GetContainingTypeDeclaration(
                     semanticModel.SyntaxTree.GetRoot(),
                     plusEqualsToken.SpanStart) as BaseTypeDeclarationSyntax;