Custom error messages with ValidationSummary in ASP.NET

Sometimes, there are problems encountered in a code-behind file that don’t warrant the extra work and mark-up that would otherwise be required to add CustomValidator controls to the page for displaying error messages to the user through your ValidationSummary. Wouldn’t it be nice if you could (somewhat) easily take care of it in your code-behind file alone, without adding additional clutter to your UserControl/Page/etc.? Well, you can! The following IValidator extension class can be added to a Page‘s Validators list with ease for displaying custom error messages.

C# code:

public class ValidationError : IValidator {
	private string _ErrorMessage;
	private bool _IsValid;
	public string ErrorMessage { get { return this._ErrorMessage; } set { this._ErrorMessage = value; } }
	public bool IsValid { get { return this._IsValid; } set { this._IsValid = value; } }
	public ValidationError(string message) { this.ErrorMessage = message; }
	public void Validate() { this.IsValid = false; }

In order to use the class in your code-behind, you just add a new instance of the ValidationError class to the Validators member of your container.

C# code:

Validators.Add(new ValidationError("There was a problem. Everybody freak out!"));

I suppose you could use this code to add the CustomValidator control anywhere you wanted to, but I generally add it to the Page‘s Validators collection and let my ValidationSummary control handle the error display.

I’ve seen a few other examples of custom classes to accomplish this purpose, but each of them was missing some vital piece that prevented it from compiling out-of-the-box. The source code in this post has been tried and tested.