How do I get an IL bytearray from a DynamicMethod?

Yeah, doesn't work, the method is generated by Reflection.Emit. The IL is stored in the MethodBuilder's ILGenerator. You can dig it out but you have to be pretty desperate. Reflection is needed to get to the internal and private members. This worked on .NET 3.5SP1:

using System.Linq.Expressions;
using System.Reflection;
using System.Reflection.Emit;
...

        var mtype = compiled.Method.GetType();
        var fiOwner = mtype.GetField("m_owner", BindingFlags.Instance | BindingFlags.NonPublic);
        var dynMethod = fiOwner.GetValue(compiled.Method) as DynamicMethod;
        var ilgen = dynMethod.GetILGenerator();
        var fiBytes = ilgen.GetType().GetField("m_ILStream", BindingFlags.Instance | BindingFlags.NonPublic);
        var fiLength = ilgen.GetType().GetField("m_length", BindingFlags.Instance | BindingFlags.NonPublic);
        byte[] il = fiBytes.GetValue(ilgen) as byte[];
        int cnt = (int)fiLength.GetValue(ilgen);
        // Dump <cnt> bytes from <il>
        //...

On .NET 4.0 you'll have to use ilgen.GetType().BaseType.GetField(...) because the IL generator was changed, DynamicILGenerator, derived from ILGenerator.

The ILReader here should work.

ILVisualizer 2010 Solution