When decompiling a single method, don't fully-qualify type names in the current namespace.

ICSharpCode.Decompiler/CSharp/Transforms/IntroduceUsingDeclarations.cs

@@ -78,7 +78,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			
 			public FindRequiredImports(TransformContext context)
 			{
-				this.currentNamespace = context.DecompiledTypeDefinition != null ? context.DecompiledTypeDefinition.Namespace : string.Empty;
+				this.currentNamespace = context.DecompiledTypeDefinition?.Namespace ?? string.Empty;
 			}
 			
 			bool IsParentOfCurrentNamespace(string ns)
@@ -123,7 +123,12 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			public FullyQualifyAmbiguousTypeNamesVisitor(TransformContext context, UsingScope usingScope)
 			{
 				this.context = new Stack<CSharpTypeResolveContext>();
-				var currentContext = new CSharpTypeResolveContext(context.TypeSystem.MainAssembly, usingScope.Resolve(context.TypeSystem.Compilation));
+				if (!string.IsNullOrEmpty(context.DecompiledTypeDefinition?.Namespace)) {
+					foreach (string ns in context.DecompiledTypeDefinition.Namespace.Split('.')) {
+						usingScope = new UsingScope(usingScope, ns);
+					}
+				}
+				var currentContext = new CSharpTypeResolveContext(context.TypeSystem.MainAssembly, usingScope.Resolve(context.TypeSystem.Compilation), context.DecompiledTypeDefinition);
 				this.context.Push(currentContext);
 				this.astBuilder = CreateAstBuilder(currentContext);
 			}