static void ThrowIfNotModel <TModel>()
{
if (!DesignUtil.ClassCache <TModel> .IsModel)
{
var error = string.Format("Type '{0}' should have '{1}' with '{2}' tag.",
typeof(TModel),
typeof(ClassDesignAttribute),
DesignUtil.ConvertTagToString(DesignTag.Model));
throw new ArgumentException(error);
}
}