remote validation attribute on viewmodel property used for both create and edit

A now I understand! There is the AdditionaFields of the Rempote attribute property where you can put the name of other properties whose values will be passes to the action method. See here an example of use of the AdditionalFields property: http://tugberkugurlu.com/archive/asp-net-mvc-remote-validation-for-multiple-fields-with-additionalfields-property

You can put in this property the principal key of the record, that you than renders into an hidden fileld.

This post shows the implementation of ASP.NET MVC Remote Validation for multiple fields with AdditionalFields property and we will validate the uniqueness of a product name under a chosen category.

   [Remote(
            "doesProductNameExistUnderCategory", 
            "Northwind", 
            AdditionalFields = "Category_ID",
            ErrorMessage = "Product name already exists under the chosen category. Please enter a different product name.",
            HttpMethod = "POST"
        )]
        [Required]
        public string Product_Name { get; set; }

As you see there, we have decorated Product_Name property with RemoteAttribute. What we need to point out here is AdditionalFields property of RemoteAttribute. Simply we are saying here that : 'Pass Category_ID value to the controller action when you try validate the Product_Name'. So, Ajax Request will send two form inputs to our action : Product_Name and Category_ID.As we have already seen on my previous blog post on ASP.NET MVC Remote Validation, Model Binder will bind those inputs to our action parameters in order to allow us to easily pick them.

Our main goal here is to check the uniqueness of the product name under the chosen category and that’s why we need Category_ID value inside our controller action. Check controller action code below and you will get what I am trying to say :

controller里面对应的action方法，需要两个参数，

public JsonResult doesProductNameExistUnderCategory(int? Category_ID, string Product_Name) {

    var model = _entities.Products.Where(x => (Category_ID.HasValue) ? 
            (x.Category_ID == Category_ID && x.Product_Name == Product_Name) : 
            (x.Product_Name == Product_Name)
        );

    return Json(model.Count() == 0);

}