gistfile1.cs

using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;

var tree = CSharpSyntaxTree.ParseText(@"
    public class MyClass
    {
        public void MyMethod()
        {
        }
    }");

var syntaxRoot = tree.GetRoot();
var MyClass = syntaxRoot.DescendantNodes().OfType<ClassDeclarationSyntax>().First();
var MyMethod = syntaxRoot.DescendantNodes().OfType<MethodDeclarationSyntax>().First();

Console.WriteLine(MyClass.Identifier.ToString());
Console.WriteLine(MyMethod.Identifier.ToString());

I had to add using System.Linq to bring .OfType() into scope