asp.net MVC3 「System.Web.Mvc.ModelClientValidationRule」問題

錯誤提示:

Error 1 The type 'System.Web.Mvc.ModelClientValidationRule' exists in both 'c:\Program Files (x86)\Microsoft ASP.NET\ASP.NET Web Pages\v2.0\Assemblies\System.Web.WebPages.dll' and 'c:\Program Files (x86)\Microsoft ASP.NET\ASP.NET MVC 3\Assemblies\System.Web.Mvc.dll' 

解決方法：

打開「.csproj」文件，將<Reference Include="System.Web.WebPages"/>
修改成：
<Reference Include="System.Web.WebPages, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL "/>