diff --git a/ICSharpCode.NRefactory.CSharp/ICSharpCode.NRefactory.CSharp.csproj b/ICSharpCode.NRefactory.CSharp/ICSharpCode.NRefactory.CSharp.csproj
index c38f7f7cf1..195a6ccb0d 100644
--- a/ICSharpCode.NRefactory.CSharp/ICSharpCode.NRefactory.CSharp.csproj
+++ b/ICSharpCode.NRefactory.CSharp/ICSharpCode.NRefactory.CSharp.csproj
@@ -269,6 +269,7 @@
+
diff --git a/ICSharpCode.NRefactory.CSharp/Refactoring/CodeIssues/ExpressionIsAlwaysOfProvidedTypeIssue.cs b/ICSharpCode.NRefactory.CSharp/Refactoring/CodeIssues/ExpressionIsAlwaysOfProvidedTypeIssue.cs
new file mode 100644
index 0000000000..8a75aad714
--- /dev/null
+++ b/ICSharpCode.NRefactory.CSharp/Refactoring/CodeIssues/ExpressionIsAlwaysOfProvidedTypeIssue.cs
@@ -0,0 +1,70 @@
+//
+// ExpressionIsAlwaysOfProvidedTypeIssue.cs
+//
+// Author:
+// Mansheng Yang
+//
+// Copyright (c) 2012 Mansheng Yang
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+using System.Collections.Generic;
+using System.Linq;
+using ICSharpCode.NRefactory.TypeSystem;
+
+namespace ICSharpCode.NRefactory.CSharp.Refactoring
+{
+ [IssueDescription ("CS0183:Given expression is always of the provided type",
+ Description = "CS0183:Given expression is always of the provided type.",
+ Category = IssueCategories.CompilerWarnings,
+ Severity = Severity.Warning,
+ IssueMarker = IssueMarker.Underline)]
+ public class ExpressionIsAlwaysOfProvidedTypeIssue : ICodeIssueProvider
+ {
+ public IEnumerable GetIssues (BaseRefactoringContext context)
+ {
+ return new GatherVisitor (context).GetIssues ();
+ }
+
+ class GatherVisitor : GatherVisitorBase
+ {
+ public GatherVisitor (BaseRefactoringContext ctx)
+ : base (ctx)
+ {
+ }
+
+ public override void VisitIsExpression (IsExpression isExpression)
+ {
+ base.VisitIsExpression (isExpression);
+
+ var type = ctx.Resolve (isExpression.Expression).Type;
+ var providedType = ctx.ResolveType (isExpression.Type);
+
+ if (type.GetAllBaseTypes ().All (t => !t.Equals (providedType)))
+ return;
+
+ var action = new CodeAction (ctx.TranslateString ("Compare with 'null'"),
+ scrpit => scrpit.Replace (isExpression, new BinaryOperatorExpression (
+ isExpression.Expression.Clone (), BinaryOperatorType.InEquality, new PrimitiveExpression (null))));
+ AddIssue (isExpression, ctx.TranslateString ("Given expression is always of the provided type. " +
+ "Consider comparing with 'null' instead"), new [] { action });
+ }
+ }
+ }
+}
diff --git a/ICSharpCode.NRefactory.Tests/CSharp/CodeIssues/ExpressionIsAlwaysOfProvidedTypeIssueTests.cs b/ICSharpCode.NRefactory.Tests/CSharp/CodeIssues/ExpressionIsAlwaysOfProvidedTypeIssueTests.cs
new file mode 100644
index 0000000000..3bb9c8f750
--- /dev/null
+++ b/ICSharpCode.NRefactory.Tests/CSharp/CodeIssues/ExpressionIsAlwaysOfProvidedTypeIssueTests.cs
@@ -0,0 +1,90 @@
+//
+// ExpressionIsAlwaysOfProvidedTypeIssueTests.cs
+//
+// Author:
+// Mansheng Yang
+//
+// Copyright (c) 2012 Mansheng Yang
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+using ICSharpCode.NRefactory.CSharp.Refactoring;
+using NUnit.Framework;
+
+namespace ICSharpCode.NRefactory.CSharp.CodeIssues
+{
+ [TestFixture]
+ public class ExpressionIsAlwaysOfProvidedTypeIssueTests : InspectionActionTestBase
+ {
+ public void Test (string variableType, string providedType)
+ {
+ var input = @"
+class TestClass
+{
+ void TestMethod (" + variableType + @" x)
+ {
+ if (x is " + providedType + @") ;
+ }
+}";
+ var output = @"
+class TestClass
+{
+ void TestMethod (" + variableType + @" x)
+ {
+ if (x != null) ;
+ }
+}";
+ Test (input, 1, output);
+ }
+
+ [Test]
+ public void TestSameType ()
+ {
+ Test ("int", "int");
+ }
+
+ [Test]
+ public void TestBaseType ()
+ {
+ Test ("int", "object");
+ }
+
+ [Test]
+ public void TestTypeParameter ()
+ {
+ var input = @"
+class TestClass
+{
+ void TestMethod (T x) where T : TestClass
+ {
+ if (x is TestClass) ;
+ }
+}";
+ var output = @"
+class TestClass
+{
+ void TestMethod (T x) where T : TestClass
+ {
+ if (x != null) ;
+ }
+}";
+ Test (input, 1, output);
+ }
+ }
+}
diff --git a/ICSharpCode.NRefactory.Tests/ICSharpCode.NRefactory.Tests.csproj b/ICSharpCode.NRefactory.Tests/ICSharpCode.NRefactory.Tests.csproj
index 833d0c0a6c..996a1d35ac 100644
--- a/ICSharpCode.NRefactory.Tests/ICSharpCode.NRefactory.Tests.csproj
+++ b/ICSharpCode.NRefactory.Tests/ICSharpCode.NRefactory.Tests.csproj
@@ -108,6 +108,7 @@
+