In the project properties tab of a C# project that targeted against msbuild 2.0 (or whatever version sharpdevelop 2 used), there is a button next to the greyed out "target framework" button labeled "Convert to C#". Pressing this gives you a dialog asking if you would liek to upgrade the cspoj, and optionally the whole solution to use msbuild 3.5 format. Also paramater substitution is not performed for ${LANG}.