I often want to test things quickly in .net without creating a new project. There are quite a few options.
REPL
Firstly the read-eval-print-loop options. These are great for quick tests.
Most of the dynamic languages have a REPL. Personally I use booish because I like the boo programming language. IronPython and IronRuby also have REPL. You can even run IronPython in your browser if you want.
The best C# REPL I’ve seen is gsharp from Mono. You can happily run Mono side by side with Microsoft’s .net frameworks. So there is no reason not to try this.
Compiling
For more complex tests a light weigh editor/compiler are useful. By far my favourite in this category is SciTE. SciTE is an incredible editor that will compile .cs files (and many others) out of the box. Just open a .cs, press F7 to compile and F5 to run. It can be configured to edit pretty much anything. Its light weigh, cross platform and it is free. IMO its an editor that every developer should take a look at.
Other options include Snippet Compiler which has a nice IDE and intellisense. Also take a look at Snippy, and the reflector snippy addin.
