Fix duplicate assembly references being added by NuGet when reference name does not have .dll or .exe file extension.

src/AddIns/Misc/PackageManagement/Project/Src/SharpDevelopProjectSystem.cs

@@ -108,7 +108,7 @@ namespace ICSharpCode.PackageManagement
 		
 		ReferenceProjectItem FindReference(string name)
 		{
-			string referenceName = Path.GetFileNameWithoutExtension(name);
+			string referenceName = GetReferenceName(name);
 			foreach (ReferenceProjectItem referenceProjectItem in project.GetItemsOfType(ItemType.Reference)) {
 				if (IsMatchIgnoringCase(referenceProjectItem.Include, referenceName)) {
 					return referenceProjectItem;
@@ -117,6 +117,22 @@ namespace ICSharpCode.PackageManagement
 			return null;
 		}
 		
+		string GetReferenceName(string name)
+		{
+			if (HasDllOrExeFileExtension(name)) {
+				return Path.GetFileNameWithoutExtension(name);
+			}
+			return name;
+		}
+		
+		bool HasDllOrExeFileExtension(string name)
+		{
+			string extension = Path.GetExtension(name);
+			return
+				IsMatchIgnoringCase(extension, ".dll") ||
+				IsMatchIgnoringCase(extension, ".exe");
+		}
+		
 		bool IsMatchIgnoringCase(string lhs, string rhs)
 		{
 			return String.Equals(lhs, rhs, StringComparison.InvariantCultureIgnoreCase);

src/AddIns/Misc/PackageManagement/Test/Src/SharpDevelopProjectSystemTests.cs

@@ -189,6 +189,45 @@ namespace PackageManagement.Tests
 			Assert.IsTrue(result);
 		}
 		
+		[Test]
+		public void ReferenceExists_ReferenceNamePassedIsInProjectAndIsReferenceNameWithNoFileExtension_ReturnsTrue()
+		{
+			CreateTestProject();
+			ProjectHelper.AddReference(project, "System.ComponentModel.Composition");
+			CreateProjectSystem(project);
+			string referenceName = "System.ComponentModel.Composition";
+			
+			bool result = projectSystem.ReferenceExists(referenceName);
+			
+			Assert.IsTrue(result);
+		}
+		
+		[Test]
+		public void ReferenceExists_ReferenceIsInProjectAndProjectReferenceSearchedForHasExeFileExtension_ReturnsTrue()
+		{
+			CreateTestProject();
+			ProjectHelper.AddReference(project, "myassembly");
+			CreateProjectSystem(project);
+			string fileName = @"D:\Projects\Test\myassembly.exe";
+			
+			bool result = projectSystem.ReferenceExists(fileName);
+			
+			Assert.IsTrue(result);
+		}
+		
+		[Test]
+		public void ReferenceExists_ReferenceIsInProjectAndProjectReferenceSearchedForHasExeFileExtensionInUpperCase_ReturnsTrue()
+		{
+			CreateTestProject();
+			ProjectHelper.AddReference(project, "myassembly");
+			CreateProjectSystem(project);
+			string fileName = @"D:\Projects\Test\MYASSEMBLY.EXE";
+			
+			bool result = projectSystem.ReferenceExists(fileName);
+			
+			Assert.IsTrue(result);
+		}
+		
 		[Test]
 		public void AddReference_AddReferenceToNUnitFramework_ProjectIsSavedAfterAddingReference()
 		{