public class GuestResponse    {        [Required(ErrorMessage = "Please enter your name")]        public string Name { get; set; }        [Required(ErrorMessage = "Please enter your email address")]        [RegularExpression(".+\\@.+\\..+", ErrorMessage = "Please enter a valid email address")]        public string Email { get; set; }        [Required(ErrorMessage = "Please enter your phone number")]        public string Phone { get; set; }        [Required(ErrorMessage = "Please specify whether you'll attend")]        public bool? WillAttend { get; set; }    }

Tip As noted earlier, I used a nullable bool for the WillAttend property. I did this so that I could apply the

Required validation attribute. If I had used a regular bool, the value I received through model binding could be only true

or false, and I wouldn’t be able to tell if the user had selected a value. A nullable bool has three possible values: true,

false, and null. The null value will be used if the user hasn’t selected a value, and this causes the Required attribute

to report a validation error. This is a nice example of how the MVC Framework elegantly blends C# features with HTML and

HTTP.

 

5.1下测试，如果不定义为 bool? ，如果未选择，绑定后值为false，但验证也未通过，实际接收的值为“”值。