在 System.Linq.Enumerable.First[TSource](IEnumerable`1 source, Func`2 predicate)
   在 Quicker.View.X.StepList.ConvertToSubProgramMenuOnClick(Object sender, RoutedEventArgs e)
   在 System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   在 System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   在 System.Windows.Controls.MenuItem.InvokeClickAfterRender(Object arg)
   在 System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   在 System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)