类库项目中特定语言资源文件的问题

I'm working on an ASP.NET MVC 2 application and use a seperate class library for my model. I used resource files in my class library project to embed validation messages and use it in my meta data classes and everything was Ok till I decided to add a new language to my project so I renamed Resource.resx to Resource.en-US.resx and also copied and saved it as a new Resource.fa-IR.resx for another language but after renaming it, everything in Designer.cs companion file has been gone and I can't access Resource file anymore. As soon as I remove the language name (e.g. en-US) from filename it works properly.I'm working on an ASP.NET MVC 2 application and