如何通过Roslyn查找基类的命名空间

using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using System;

class Program
{
    static void Main()
    {
        string sourceCode = @"
            using System;

            namespace MyNamespace
            {
                public class MyBaseClass
                {
                }

                public class MyClass : MyBaseClass
                {
                }
            }";

        SyntaxTree syntaxTree = CSharpSyntaxTree.ParseText(sourceCode);
        var root = syntaxTree.GetRoot();

        var classDeclaration = root.DescendantNodes()
                                   .OfType<ClassDeclarationSyntax>()
                                   .FirstOrDefault();

        if (classDeclaration != null)
        {
            var baseType = classDeclaration.BaseList?.Types.FirstOrDefault()?.Type;
            if (baseType != null)
            {
                var namespaceDeclaration = baseType.Ancestors()
                                                   .OfType<NamespaceDeclarationSyntax>()
                                                   .FirstOrDefault();
                if (namespaceDeclaration != null)
                {
                    var namespaceName = namespaceDeclaration.Name.ToString();
                    Console.WriteLine("Base class namespace: " + namespaceName);
                }
            }
        }
    }
}