private static Delegate /*!*/ CompileDebug(LambdaExpression /*!*/ lambda)
 {
     // try to use PDBs and fallback to CustomGenerator if not allowed to:
     if (_HasPdbPermissions)
     {
         try {
             return(CompilerHelpers.CompileToMethod(lambda, DebugInfoGenerator.CreatePdbGenerator(), true));
         } catch (SecurityException) {
             // do not attempt next time in this app-domain:
             _HasPdbPermissions = false;
         }
     }
     return(CompilerHelpers.CompileToMethod(lambda, new CustomGenerator(), false));
 }