use pattern matching

src/Features/CSharp/Portable/CodeFixes/Suppression/CSharpSuppressionCodeFixProvider.cs

@@ -67,8 +67,7 @@ protected override SyntaxTriviaList CreatePragmaRestoreDirectiveTrivia(Diagnosti
 
         protected override bool IsAttributeListWithAssemblyAttributes(SyntaxNode node)
         {
-            var attributeList = node as AttributeListSyntax;
-            return attributeList != null &&
+            return node is AttributeListSyntax attributeList &&
                 attributeList.Target != null &&
                 attributeList.Target.Identifier.Kind() == SyntaxKind.AssemblyKeyword;
         }
@@ -185,8 +184,7 @@ protected override bool IsSingleAttributeInAttributeList(SyntaxNode attribute)
         {
             if (attribute is AttributeSyntax attributeSyntax)
             {
-                var attributeList = attributeSyntax.Parent as AttributeListSyntax;
-                return attributeList != null && attributeList.Attributes.Count == 1;
+                return attributeSyntax.Parent is AttributeListSyntax attributeList && attributeList.Attributes.Count == 1;
             }
 
             return false;

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

@@ -2064,8 +2064,7 @@ public override SyntaxNode SetCanOverride(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();
             }
@@ -2132,8 +2131,7 @@ public override EnvDTE80.vsCMConstKind GetConstKind(SyntaxNode variableNode)
                 return EnvDTE80.vsCMConstKind.vsCMConstKindConst;
             }
 
-            var member = GetNodeWithModifiers(variableNode) as MemberDeclarationSyntax;
-            if (member == null)
+            if (!(GetNodeWithModifiers(variableNode) is MemberDeclarationSyntax member))
             {
                 throw Exceptions.ThrowEFail();
             }
@@ -2945,8 +2943,7 @@ public override Document Delete(Document document, SyntaxNode node)
 
         public override string GetMethodXml(SyntaxNode node, SemanticModel semanticModel)
         {
-            var methodDeclaration = node as MethodDeclarationSyntax;
-            if (methodDeclaration == null)
+            if (!(node is MethodDeclarationSyntax methodDeclaration))
             {
                 throw Exceptions.ThrowEUnexpected();
             }
@@ -3758,10 +3755,9 @@ public override object GetTypeExtender(string name, AbstractCodeType symbol)
 
         protected override bool AddBlankLineToMethodBody(SyntaxNode node, SyntaxNode newNode)
         {
-            var methodDeclaration = node as MethodDeclarationSyntax;
             var newMethodDeclaration = newNode as MethodDeclarationSyntax;
 
-            return methodDeclaration != null
+            return node is MethodDeclarationSyntax methodDeclaration
                 && methodDeclaration.Body == null
                 && newMethodDeclaration != null
                 && newMethodDeclaration.Body != null;

src/Workspaces/CSharp/Portable/Extensions/AttributeArgumentSyntaxExtensions.cs

@@ -29,8 +29,7 @@ internal static class AttributeArgumentSyntaxExtensions
                 return null;
             }
 
-            var argumentList = argument.Parent as AttributeArgumentListSyntax;
-            if (argumentList == null)
+            if (!(argument.Parent is AttributeArgumentListSyntax argumentList))
             {
                 return null;
             }

src/Workspaces/CSharp/Portable/Formatting/Rules/IndentBlockFormattingRule.cs

@@ -46,8 +46,7 @@ private void AddTypeParameterConstraintClauseOperation(List<IndentBlockOperation
 
         private void AddSwitchIndentationOperation(List<IndentBlockOperation> list, SyntaxNode node, OptionSet optionSet)
         {
-            var section = node as SwitchSectionSyntax;
-            if (section == null)
+            if (!(node is SwitchSectionSyntax section))
             {
                 return;
             }

src/Workspaces/CSharp/Portable/Utilities/FormattingRangeHelper.cs

@@ -392,9 +392,8 @@ private static SyntaxNode GetTopContainingNode(SyntaxNode node)
 
         public static bool IsColonInSwitchLabel(SyntaxToken token)
         {
-            var switchLabel = token.Parent as SwitchLabelSyntax;
             return token.Kind() == SyntaxKind.ColonToken &&
-                switchLabel != null &&
+                token.Parent is SwitchLabelSyntax switchLabel &&
                 switchLabel.ColonToken == token;
         }