Preprocessor to make C# code for WPF compatible with NoesisGUI (replace System.Windows namespaces)

RoslynWpfToNoesisPreprocessor.cs

public static SyntaxNode ProcessSyntaxTree(
            SyntaxTree syntaxTree,
            ConcurrentStack<Diagnostic> syntaxTreeProcessingMessages)
        {
            var replacementsDict = new Dictionary<SyntaxNode, SyntaxNode>(0);
            var root = (CompilationUnitSyntax)syntaxTree.GetRoot();

            foreach (var usingNode in root.DescendantNodes().OfType<UsingDirectiveSyntax>())
            {
                var ns = usingNode.Name.GetText().ToString();
                if (ns.StartsWith("System.Windows", StringComparison.Ordinal))
                {
                    SyntaxNode replacement = usingNode.WithName(SyntaxFactory.IdentifierName("Noesis"));
                    replacementsDict.Add(usingNode, replacement);
                    continue;
                }
            }

            var qualifiedNameNodes = root.DescendantNodes().OfType<QualifiedNameSyntax>();
            foreach (var qualifiedNameNode in qualifiedNameNodes)
            {
                var nsLeft = qualifiedNameNode.Left.GetText().ToString();

                if (nsLeft.StartsWith("System.Windows", StringComparison.Ordinal))
                {
                    var replacement =
                        SyntaxFactory.IdentifierName("Noesis");

                    replacementsDict.Add(qualifiedNameNode, replacement);
                    continue;
                }
            }

            if (replacementsDict.Count <= 0)
            {
                // not modified
                return null;
            }

            root = root.ReplaceNodes(replacementsDict.Keys, (n1, n2) => replacementsDict[n1]);
            return root;
        }