MVC model validation for email from database in asp.net

There are many cases where we need to validate the value in controls before submitting to the database, so let's discuss email validation like format, length and existence into database. We will walk through in this article, how to validate entered user email from database, whether email is already exists in database if yes then show error to user that email already taken by some one, if no email found in database then allow user to create the account.

To validate the required field in MVC we user

[Required(ErrorMessage = "{0} is required!")]    
[Display(Name = "Email")]
public string Email { get; set; }

if you will try to submit the page without entering any thing it will show the error "Email is required!"

To check email format add this

[DataType(DataType.EmailAddress)]
[RegularExpression(@"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*", 
    ErrorMessage = "Invalid email")]

Some times we need to validate email from database, like when we allow user to create an account only with a valid email id and which is not already taken then there should be some way to validate email from database once user left the email field then we can use following annotation

[Remote("CheckUserName", "User", ErrorMessage = "Already in use")]

Here CheckUserName is the action and User is the controller name

Let's see the full method which can return result in json format

 public JsonResult CheckUserName(string Email)
 {
   MyDataContext db = new MyDataContext();
   var result = true;
   var user = db.Users.Where(x=>x.Email == Email).FirstOrDefault();

   if(user != null)
       result = false;

   return Json(result, JsonRequestBehavior.AllowGet);
 }

That's all we need to set to validate the email from database

Once you will leave the email text box it will validate entered email from database, here is the complete code

    [Required(ErrorMessage = "{0} required")]
    [DataType(DataType.EmailAddress)]
    [Display(Name = "Email")]
    [RegularExpression(@"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*", 
         ErrorMessage = "Invalid email")]
    [Remote("CheckUserName", "User", ErrorMessage = "Already in use!")]       
    [StringLength(100, ErrorMessage = "{0}: 100 is the limit")]
    public string Email { get; set; }

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