Compare compiled .NET assemblies?

Solution 1:

Ways to Compare .NET Assemblies suggests

Commercial:

• NDepend

Free:

• JustAssembly (only shows differences in API)
• BitDiffer (same)
• Reflector Diff Add-in (which you've already discovered, but not available anymore)

Existing compare tools like Beyond Compare (commercial) can do this by special configuration. Here's how to do this for Beyond Compare:

• Go to Tools → Options
• Click New.., select "Text format", click OK
• Give it a name (say, EXE, or DLL), and specify the mask as *.exe or *.dll
• Click on tab Conversion and select "External program (Unicode filenames)"
• Under "Loading", specify the path to ildasm and add %s /OUT:%t /NOBAR (i.e.: C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.8 Tools\ildasm.exe %s /OUT:%t /NOBAR)
• Make sure to check disable editing.
• Click Save, then Close
• Restart BC and open two exe files to compare, it should decompile into ilasm automatically now.

You can also add syntax highlighting to this new format. I plan to send the syntax file to them so that it'll become available to share.

Solution 2:

Two ways.

You could ILDASM and diff with classic tools.

Or you could use NDepends, which will cost for that feature.

[Piece to C# bloaters..]

Solution 3:

I just had to compare two revisions of the same DLL, which had the same version (I needed to implement a small hotfix, and deploy the DLL in production, but I wanted to make sure that no other changes leaked into code). Ideally, I would want the Assemby Diff add-in to show me the difference, but it does not work (it thinks that I'm comparing a DLL to itself). So this is what I did:

• Created two folders to hold disassembled source files.
• Used the Reflector's Export option (from context menu) to generate source files from each DLL in the folders created in previous step.
• Used the free DiffMerge tool to compare two directories; the tools showed me the modified files and the difference.

It's a bit kludgy, but seems to work. I wish the Assembly Diff add-in worked, though.

UPDATE: The latest version of the Assembly Diff add-in is supposed to fix the issue of comparing two versions of the same assembly. Give it a try.

Solution 4:

The tool NDepend offers many features to handle .NET code diff. Disclaimer: I am one of the developer of the tool.

The panel Search by Change is dedicated to browse assemblies code diff. Notice that:

• You can plug to NDepend any code diff tool used by the menu Compare older and newer version of source file
• If you don't have the source code, only the raw assemblies, there is the option Compare older and newer version disassembled with Reflector

Notice also in the screenshot that a CQLinq code query is generated to browse the diff.

from m in Application.Methods 
where m.CodeWasChanged() 
select new { m, m.NbLinesOfCode }

Many others default diff queries and rules are proposed by default, that will let you browse .NET code diff in a smart way.

• Types that used to be 100% covered but not anymore
• API Breaking Changes: Methods
• Avoid making complex methods even more complex
• Avoid decreasing code coverage by tests of types
• From now, all types added or refactored should respect basic quality principles
• Avoid transforming an immutable type into a mutable one
• Heuristic to find types moved from one namespace or assembly to another