Avoid race conditions in WPF bindings by postemptively retesting before allowing OnExecute to continue.

Author: comintern

Rubberduck.Core/UI/Command/ReparseCommand.cs

@@ -46,6 +46,14 @@ protected override bool EvaluateCanExecute(object parameter)
 
         protected override void OnExecute(object parameter)
         {
+            // WPF binds to EvaluateCanExecute asychronously, which means that in some instances the bound refresh control will
+            // enable itself based on a "stale" ParserState. There's no easy way to test for race conditions inside WPF, so we
+            // need to make this test again...
+            if (!EvaluateCanExecute(parameter))
+            {
+                return;
+            }
+
             if (_settings.CompileBeforeParse)
             {
                 if (!VerifyCompileOnDemand())