Custom data validation using data annotations

CustomValidation.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq;

[MetadataType(typeof (FooBarMetaData))]
public class FooBar
{
	// Insert FooBar related properties, methods, etc. here

	private sealed class FooBarMetaData
	{
		[DisplayName("First Name")]
		[Required(ErrorMessage = "<b>First Name</b> is required")]
		[StringLength(50, ErrorMessage = "<b>First Name</b> cannot exceed 50 characters")]
		public string FirstName{ get; set; }

		[DisplayName("Last Name")]
		[Required(ErrorMessage = "<b>Last Name</b> is required")]
		[StringLength(50, ErrorMessage = "<b>Last Name</b> cannot exceed 50 characters")]
		public string LastName{ get; set; }

		[DisplayName("Email")]
		[Required(ErrorMessage = "<b>Email</b> is required")]
		[EmailValidator(ErrorMessage = "Invalid email address")]
		public string EmailAddress{ get; set; }

		[DisplayName("Location")]
		[Required(ErrorMessage = "<b>Location</b> is required")]
		[StringLength(50, ErrorMessage = "<b>Location</b> cannot exceed 50 characters")]
		public string Location{ get; set; }
	}
}

public class EmailValidatorAttribute : ValidationAttribute
{
	public override bool IsValid(object value)
	{
		if (value == null)
			return false;

		bool isValidEmail;

		// Insert logic here to validate the email address
		
		return isValidEmail;
	}
}