Normally I work with Visual Studio and also debug with visual studio. But we have virtual machines in another network there is Visual Studio not installed. And I can not remote debug. To install every time Visual Studio is in my eyes a overhead.
So I look for a small debugger for managed (c#) code that I can copy into the virtual machines to set breakpoints, step through the source code, see exceptions.
Knows someone a small debugger for managed code?
There is mdbg - it is harder to use (evaluator has a strange syntax) but on the other hand it is super-lightweight. You may get it from Windows 7 SDK (I don't know why they remove it from Win 8 SDK): c:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Bin\NETFX 4.0 Tools\
(x64 for 64-bit - you will need mdbg.exe and mdbgcore.dll) or compile it by yourself using source code from here: http://www.microsoft.com/en-us/download/details.aspx?id=2282. Make sure that you choose the correct bitness. I used it with success in production environments (also for .NET4.5 applications) and even created 2 extensions for it - maybe you will find them useful:
If mdbg is not enough and you need to get deeper (analyze GC Heap, .NET iternals etc.) you probably will need to learn windbg (it's also xcopy deployed and you can get it from Windows Debugging Toolkit).