Using DataAnnotations to compare two model properties

Question

How would I go about writing a custom ValidationAttribute that compares two fields? This is the common "enter password", "confirm password" scenario. I need to be sure the two fields are equal and to keep things consistent, I want to implement the validation via DataAnnotations.

So in pseudo-code, I'm looking for a way to implement something like the following:

public class SignUpModel {     [Required]     [Display(Name = "Password")]     public string Password { get; set; }      [Required]     [Display(Name = "Re-type Password")]     [Compare(CompareField = Password, ErrorMessage = "Passwords do not match")]     public string PasswordConfirm { get; set; } }  public class CompareAttribute : ValidationAttribute {     public CompareAttribute(object propertyToCompare)     {         // ??     }      public override bool IsValid(object value)     {         // ??     } } 

So the question is, how do I code the [Compare] ValidationAttribute?

Answer 1

Make sure that your project references system.web.mvc v3.xxxxx.

Then your code should be something like this:

using System.Web.Mvc; 

. . . .

[Required(ErrorMessage = "This field is required.")]     public string NewPassword { get; set; }  [Required(ErrorMessage = "This field is required.")] [Compare(nameof(NewPassword), ErrorMessage = "Passwords don't match.")] public string RepeatPassword { get; set; }