阅读目录:

一. CheckBox必选验证的困局

二. 对于服务端ValidationAttribute的实现分析

三. 自定义EnforceTrueAttribute实现服务器端验证

四. 添加客户端验证

五. 总结

public class RegisterModel { [DisplayName("User Name")] [Required(ErrorMessage = "User Name is required")] public String UserName { get; set; }[Required] public bool IsAgreeTerm { get; set; }}

@using (Html.BeginForm()) { @Html.AntiForgeryToken() @Html.ValidationSummary()<fieldset> <legend>Registration Form</legend> <ol> <li> @Html.LabelFor(m => m.EmployeeName) @Html.EditorFor(m => m.EmployeeName) <br/> @Html.ValidationMessageFor(m => m.EmployeeName) </li> <li> @Html.LabelFor(m => m.IsAgreeTerm) @Html.EditorFor(m => m.IsAgreeTerm) <br/> @Html.ValidationMessageFor(m => m.IsAgreeTerm) </li> </ol> <input type="submit" value="Register" /> </fieldset>
}

public class EnforceTrueAttribute : ValidationAttribute { public override bool IsValid(object value) { if (value == null) return false; if (value.GetType() != typeof(bool)) throw new InvalidOperationException("can only be used on boolean properties."); return (bool)value; }public override string FormatErrorMessage(string name) { return "The " + name + " field must be checked in order to continue."; }}

[DisplayName("Term")]
[EnforceTrue]
public bool IsAgreeTerm { get; set; }

public class EnforceTrueAttribute : ValidationAttribute, IClientValidatable
{ public override bool IsValid(object value) { if (value == null) return false; if (value.GetType() != typeof(bool)) throw new InvalidOperationException("can only be used on boolean properties."); return (bool)value; }public override string FormatErrorMessage(string name) { return "The " + name + " field must be checked in order to continue."; }public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context) { yield return new ModelClientValidationRule { ErrorMessage = String.IsNullOrEmpty(ErrorMessage) ? FormatErrorMessage(metadata.DisplayName) : ErrorMessage, ValidationType = "enforcetrue" }; }
}

<script type="text/javascript"> jQuery.validator.addMethod("enforcetrue", function(value, element, param) { return element.checked; }); jQuery.validator.unobtrusive.adapters.addBool("enforcetrue"); </script>