How to Implement Remote Validation in ASP.Net MVC

Introduction

For some of our web applications we must validate the uniqueness of a field, for example when we create a user for the application then the user Id must be unique in order to provide login capability for the system. To do this we need to write code to make a remote server call to validate the field.

ASP.NET MVC provides a mechanism that can make a remote server call to validate the field without posting the entire form to the server. The "Remote" validation attribute is useful for that. This attribute is useful when we have a field that cannot be validated on the client side so we must validate it on to the server side.

Remote Attribute

The Remote attribute class uses the jQuery validation plug-in remote validator. With remote attribute, we need to pass a route name (to validate the text on the server side) or pass an action and controller name. This attribute enables a client-side validation and makes a call to the server when the actual validation is done.

For example, I want to create a customer registration form and it has a user id that must be unique within the database. I want to validate this user id using a remote attribute. The Following is the procedure to use a remote attribute in this case.


Step 1

Create a model for the customer and apply the report validation for the column user id.

public class Customer
{
    public int CustomerId
    {
        get;
        set;
    }
    public string Name
    {
        get;
        set;
    }
    [RemoteAttribute("IsUserExists", "Home")]
    public string UserId
    {
        get;
        set;
    }
}

Step 2

Create a method in the controller to check the validation. This controller's action method must return a JsonResult object (true or false) depending on the validation performed.

public class HomeController: Controller
{
    public JsonResult IsUserExists(string userId)
    {
        return IsExist(userId) ? Json(true, JsonRequestBehavior.AllowGet) : Json(false, JsonRequestBehavior.AllowGet);
    }

    public bool IsExist(string userId)
    {
        // Write code to validate UserId weather is Userid already exists or not and base on return true and false.
        if (string.IsNullOrEmpty(userId)) return false;
        else if (userId == "jignesh") return false;
        else return true;
    }

}

Output

 

Pass Additional parameter

We can also send additional parameters from the screen by setting the additional field property. In the following example I want “name” properties along with a “UserId” property, so I have set an additional field property to “name".

[RemoteAttribute("IsUserExists", "Home",AdditionalFields="Name")]
public string UserId { get; set; }

We can get multiple additional properties by passing property names separated by commas into the AdditionalFields property of the remote attribute.

[RemoteAttribute("IsUserExists", "Home", AdditionalFields = "Name,Address”)]
public string UserId { get; set; }

Customize error message

We can also customize the error message by passing the named parameter “ErrorMessage”. By default the message is “{property Name} is invalid”. Using this named property we can change the error message text.

[RemoteAttribute("IsUserExists", "Home", ErrorMessage = "This UserId is already in use.")]
public string UserId { get; set; }

I hope this helps!