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.

  1. public class Customer
  2. {
  3. public int CustomerId
  4. {
  5. get;
  6. set;
  7. }
  8. public string Name
  9. {
  10. get;
  11. set;
  12. }
  13. [RemoteAttribute("IsUserExists", "Home")]
  14. public string UserId
  15. {
  16. get;
  17. set;
  18. }
  19. }
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.
  1. public class HomeController: Controller
  2. {
  3. public JsonResult IsUserExists(string userId)
  4. {
  5. return IsExist(userId) ? Json(true, JsonRequestBehavior.AllowGet) : Json(false, JsonRequestBehavior.AllowGet);
  6. }
  8. public bool IsExist(string userId)
  9. {
  10. // Write code to validate UserId weather is Userid already exists or not and base on return true and false.
  11. if (string.IsNullOrEmpty(userId)) return false;
  12. else if (userId == "jignesh") return false;
  13. else return true;
  14. }
  16. }
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".
  1. [RemoteAttribute("IsUserExists", "Home",AdditionalFields="Name")]
  2. 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.
  1. [RemoteAttribute("IsUserExists", "Home", AdditionalFields = "Name,Address”)]
  2. 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.
  1. [RemoteAttribute("IsUserExists", "Home", ErrorMessage = "This UserId is already in use.")]
  2. public string UserId { get; set; }
I hope this helps!