How do I create a dll/exe off a previously diassembled .il file?

You can create a dll/exe from the il file using the ilasm.exe utility. This utility is usually installed in the C:\WINNT\Microsoft.NET\Framework\v1.0.3705 (or the appropriate version no.) directory.

If you want to run this utility via command line it would help if you add the above path to your Environment Path variable.

Here is an example command line:

// The .res resource file is optional
ilasm TextProcessing.il /dll /output:TextProcessing.dll /resource:TextProcessing.res