There are various tools available to compare .net assemblies. Most of them are paid version or requires lot of efforts to find code level differences between two assemblies or DLLs. If you want to find out what has changed between two version of the same DLL, here are the steps how you can do that using free tools.
- Download ILSpy. ILSpy is the open-source .NET assembly browser and decompiler.
- Download DiffMerge. DiffMerge is an application to visually compare and merge files.
- Open ILSpy and then open DLLs that you want to compare by clicking on File -> Open and choose DLL.
- Select the assembly and click File -> Save Code to save decompiled code of assembly. Repeat the same step for another assembly that you want to compare.
- Open DiffMerge and click on File -> Open Folder Diff.
- Select two folders where you have saved source code of assemblies in step# 4 and then click “Ok”.
It will show you the list of files that has changed between two versions. If you double click on a file, it will show the code difference between two files.
Hope this helps.