When I run the following code I would suspect a null reference exception to
be thrown:

param1 = null;
int x = param1.Length;

However, when I compile this code dynamically into a class and method a null
reference exception is ONLY thrown if the debugger is attached????  Otherwise
no exception is thrown.  Can someone please explain this?  I included the
code below - create a console application and overwrite the existing class
with the code below.

CODE TO REPRODUCE:

using System;
using System.CodeDom.Compiler;
using System.Reflection;
using Microsoft.CSharp;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Assembly a = CreateAssembly();
            object o = a.CreateInstance("ConsoleApplication1.TestClass");
            MethodInfo info = o.GetType().GetMethod("RunMe");
            info.Invoke(o, new object[] { null });
        }

        private static Assembly CreateAssembly()
        {
            string src = @"
                namespace ConsoleApplication1
                {
                    using System;

                    public class TestClass
                    {
                        public virtual void RunMe(string param1)
                        {
                            int x = param1.Length;
                        }
                    }
                }";

            CodeDomProvider provider = new CSharpCodeProvider();
            CompilerParameters compilerParameters = new CompilerParameters();
            compilerParameters.GenerateInMemory = true;
            compilerParameters.IncludeDebugInformation = false;
            compilerParameters.GenerateExecutable = false;

            CompilerResults results =
provider.CompileAssemblyFromSource(compilerParameters,
                src);

            return results.CompiledAssembly;
        }
    }
}