CS0006: 未能找到元数据文件 是什么意思？

编译器错误信息: CS0006: 未能找到元数据文件“c:\windows\microsoft.net\framework\v1.1.4322\temporary asp.net files\020job\af4c287f\8df71a07\assembly\dl2\41d43779\a6f9a3f7_4cbbc401\accountsbusiness.dll”


我在Global.asax.cs中
protected void Application_AuthenticateRequest(Object sender, EventArgs e)
{
if(HttpContext.Current.User!=null)
{
if (Context.User.Identity.IsAuthenticated)
{
if (Context.User is JobPrincipal)
{
JobPrincipal newUser = new JobPrincipal( Context.User.Identity.Name );
Context.User = newUser;
}
}
}
}
JobPrincipal是我自己定义的class