“无法找到名称为{Locator}的资源”使用mvvm-light用户控件时出错

i am using the mvvm light toolkit to create a WPF application. I created a user control and a corresponding ViewModel. I created a ViewModel property in the ViewModelLocator. I bound the user controls datacontext to the property in the Locator class. When i edit the User Control in Blend or the VS Designer everything seems to work, since i can see my design time data.i am using the mvvm light toolkit to create a W