Remote Validation on a Dropdown List Combination in MVC 5

Question

Does anyone know how I can perform remote validation on a drop-down list combination in MVC 5?

In short, I assign a customer to a user so I want to ensure that a customer can't be assigned to the same user twice.

I have created a validation action in my controller, but it does not work. It tells me that the customer has been assigned to the user regardless of the combination even when the combination does not exist in the database.

Here is what my model looks like:

public class UserCustomer : BaseAttributes
{
    [Key]
    public int UserCustomerID { get; set; }
    [Remote("CustomerAssignedToUser", "UserCustomer", AdditionalFields = "ApplicationUserID", ErrorMessage = "The customer has already been assigned to the selected user!")]
    public int CustomerID { get; set; }
    public virtual Customer Customer { get; set; }
    public int ApplicationUserID { get; set; }
    public virtual ApplicationUser ApplicationUser { get; set; }
}

Here is the validation action in my controller:

public JsonResult CustomerAssignedToUser(int CustomerID, int ApplicationUserID)
{
    return Json(!db.UserCustomers.Any(x => x.CustomerID == CustomerID && x.ApplicationUserID == ApplicationUserID), JsonRequestBehavior.AllowGet);
}

Here are the two drop-down lists in my view:

@Html.DropDownListFor(model => model.CustomerID, new SelectList((System.Collections.IEnumerable)ViewData["CustomerID"], "Value", "Text"), htmlAttributes: new { @class = "form-control" })
@Html.ValidationMessageFor(model => model.CustomerID, "", new { @class = "text-danger" })

@Html.DropDownListFor(model => model.ApplicationUserID, new SelectList((System.Collections.IEnumerable)ViewData["ApplicationUserID"], "Value", "Text"), htmlAttributes: new { @class = "form-control" })
@Html.ValidationMessageFor(model => model.ApplicationUserID, "", new { @class = "text-danger" })

Help will be appreciated. I for the life of me can't see what is wrong with my code.

Do you send AJAX request to the backend? If yes, could you please share how you do it? — Dmitresky, Jan 29 '19 at 19:53
@M . Anthony, Found nothing wrong in your provided code. Have to debug it properly so see what actually happening! — TanvirArjel, Jan 30 '19 at 03:00

score 0 · Answer 1 · answered Jan 30 '19 at 18:03

I have managed to solve the issue. The solution was quite simple. All I had to do was implement the same data annotation in reverse on the additional field inside the model like this:

[Remote("CustomerAssignedToUser", "UserCustomer", AdditionalFields = "ApplicationUserID", ErrorMessage = "The customer has already been assigned to the selected user!")]
        public int CustomerID { get; set; }

[Remote("CustomerAssignedToUser", "UserCustomer", AdditionalFields = "CustomerID", ErrorMessage = "The customer has already been assigned to the selected user!")]
        public int ApplicationUserID { get; set; }

I find that it does not work as well with dropdown lists though as it does not always update immediately and can at times take multiple switches in the dropdown lists to validate correctly. It might be because the ID's are int values and not GUID's. The method works perfectly when using strings and text box inputs for example validating a first name and last name combination.

Remote Validation on a Dropdown List Combination in MVC 5

1 Answers1