C# monkey patching - is it possible?

Question

Is it possible to write a C# assembly which when loaded will inject a method into a class from another assembly? If yes, will the injected method be available from languages using DLR, like IronPython?

namespace IronPython.Runtime
{
    public class Bytes : IList<byte>, ICodeFormattable, IExpressionSerializable
    {
        internal byte[] _bytes;

        //I WANT TO INJECT THIS METHOD
        public byte[] getbytes()
        {
            return _bytes;
        }
    }
}

I need that method, and I would like to avoid recompiling IronPython if possible.

Answer 1

you can use reflection to get this method into another assembly

i dont know about IronPython but i think this will help you

http://www.voidspace.org.uk/ironpython/dynamically_compiling.shtml

Answer 2

I don't believe that it's possible to extend an existing .NET type once it's created.

If all you need is a byte[] (in IronPython, I presume), you can do:

>>> import clr
>>> import System
>>> b = bytes([1, 2, 3, 4])
>>> a = System.Array[bytes](b)
>>> a
Array[bytes]((b'\x01', b'\x02', b'\x03', b'\x04'))

However, it's unlikely that IronPython will ever allow access to Bytes' underlying storage (unless CPython does), as it's not safe.

Answer 3

This can be done with frameworks such as TypeMock, which hook into the framework profiling APIs.

However this kind of injection is usually only used to facilitate unit testing rather than within production code and comes with a performance hit. My opinion is that if you are having to do something as drastic as this outside of unit testing, then do you are probably doing something wrong.

Answer 4

It is possible to access extension methods from IronPython. See http://blogs.msdn.com/saveenr/archive/2008/11/14/consuming-extension-methods-in-ironpython.aspx