FAQ: Technical - Mono: "What is a 100% .NET application?

A '100% .NET application' is one that only uses the APIs defined under the System namespace and does not use P/Invoke. These applications would in theory run unmodified on Windows, Linux, HP-UX, Solaris, MacOS X and others. Note that this requirement also holds for all assemblies used by the application. If one of them is Windows-specific, then the entire program is not a 100% .NET application. Furthermore, a 100% .NET application must not contain non-standard data streams in the assembly. For example, Visual Studio .NET will insert a #- stream into assemblies built under the 'Debug' target. This stream contains debugging information for use by Visual Studio .NET; however, this stream can not be interpreted by Mono (unless you're willing to donate support). Thus, it is recommended that all Visual Studio .NET-compiled code be compiled under the Release target before it is executed under Mono."