dnSpy is a debugger and .NET assembly editor. You can use it to edit and debug assemblies even if you don't have any source code available. Main features:

• Debug .NET and Unity assemblies
• Edit .NET and Unity assemblies
• Light and dark themes

See below for more features

https://github.com/dnSpy/dnSpy/releases

git clone --recursive https://github.com/dnSpy/dnSpy.git
cd dnSpy
# or dotnet build
./build.ps1 -NoMsbuild

To debug Unity games, you need this repo too: https://github.com/dnSpy/dnSpy-Unity-mono (or get the binaries from https://github.com/dnSpy/dnSpy/releases/unity)

• Debug .NET Framework, .NET and Unity game assemblies, no source code required
• Set breakpoints and step into any assembly
• Locals, watch, autos windows
• Variables windows support saving variables (eg. decrypted byte arrays) to disk or view them in the hex editor (memory window)
• Object IDs
• Multiple processes can be debugged at the same time
• Break on module load
• Tracepoints and conditional breakpoints
• Export/import breakpoints and tracepoints
• Call stack, threads, modules, processes windows
• Break on thrown exceptions (1st chance)
• Variables windows support evaluating C# / Visual Basic expressions
• Dynamic modules can be debugged (but not dynamic methods due to CLR limitations)
• Output window logs various debugging events, and it shows timestamps by default :)
• Assemblies that decrypt themselves at runtime can be debugged, dnSpy will use the in-memory image. You can also force dnSpy to always use in-memory images instead of disk files.
• Public API, you can write an extension or use the C# Interactive window to control the debugger

• All metadata can be edited
• Edit methods and classes in C# or Visual Basic with IntelliSense, no source code required
• Add new methods, classes or members in C# or Visual Basic
• IL editor for low-level IL method body editing
• Low-level metadata tables can be edited. This uses the hex editor internally.

• Click on an address in the decompiled code to go to its IL code in the hex editor
• The reverse of the above, press F12 in an IL body in the hex editor to go to the decompiled code or other high-level representation of the bits. It's great to find out which statement a patch modified.
• Highlights .NET metadata structures and PE structures
• Tooltips show more info about the selected .NET metadata / PE field
• Go to position, file, RVA
• Go to .NET metadata token, method body, #Blob / #Strings / #US heap offset or #GUID heap index
• Follow references (Ctrl+F12)

• BAML decompiler
• Blue, light and dark themes (and a dark high contrast theme)
• Bookmarks
• C# Interactive window can be used to script dnSpy
• Search assemblies for classes, methods, strings, etc
• Analyze class and method usage, find callers, etc
• Multiple tabs and tab groups
• References are highlighted, use Tab / Shift+Tab to move to the next reference
• Go to the entry point and module initializer commands
• Go to metadata token or metadata row commands
• Code tooltips (C# and Visual Basic)
• Export to project

• ILSpy decompiler engine (C# and Visual Basic decompilers)
• Roslyn (C# and Visual Basic compilers)
• dnlib (.NET metadata reader/writer which can also read obfuscated assemblies)
• VS MEF (Faster MEF equals faster startup)
• ClrMD (Access to lower level debugging info not provided by the CorDebug API)
• Iced (x86/x64 disassembler)

Click here if you want to help with translating dnSpy to your native language.

See the Wiki for build instructions and other documentation.

dnSpy is licensed under GPLv3.