解决Revit开发程序运行时，按ESC退出报错问题

对特定的异常进行捕获和报错 

try
{
    var reference = uidoc.Selection.PickObject(ObjectType.Element, "请选择您要查看的元素");
}
catch (Autodesk.Revit.Exceptions.OperationCanceledException ex)
{
    TaskDialog.Show("ERROR", "未选取任何对象！");
    //TaskDialog.Show("ERROR",ex.ToString());
    return Result.Failed;
}