Here's a sample illustrating how you could proceed to implement a custom validation attribute:
public class NotEqualAttribute : ValidationAttribute, IClientValidatable
{
public string OtherProperty { get; private set; }
public NotEqualAttribute(string otherProperty)
{
OtherProperty = otherProperty;
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
var property = validationContext.ObjectType.GetProperty(OtherProperty);
if (property == null)
{
return new ValidationResult(
string.Format(
CultureInfo.CurrentCulture,
"{0} is unknown property",
OtherProperty
)
);
}
var otherValue = property.GetValue(validationContext.ObjectInstance, null);
if (object.Equals(value, otherValue))
{
return new ValidationResult(FormatErrorMessage(validationContext.DisplayName));
}
return null;
}
public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
{
var rule = new ModelClientValidationRule
{
ErrorMessage = ErrorMessage,
ValidationType = "notequalto",
};
rule.ValidationParameters["other"] = OtherProperty;
yield return rule;
}
}
and then on the model:
public class MyViewModel
{
public string Prop1 { get; set; }
[NotEqual("Prop1", ErrorMessage = "should be different than Prop1")]
public string Prop2 { get; set; }
}
controller:
public class HomeController : Controller
{
public ActionResult Index()
{
return View(new MyViewModel
{
Prop1 = "foo",
Prop2 = "foo"
});
}
[HttpPost]
public ActionResult Index(MyViewModel model)
{
return View(model);
}
}
and view:
@model MyViewModel
<script src="@Url.Content("~/Scripts/jquery.validate.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.js")" type="text/javascript"></script>
<script type="text/javascript">
jQuery.validator.unobtrusive.adapters.add(
'notequalto', ['other'], function (options) {
options.rules['notEqualTo'] = '#' + options.params.other;
if (options.message) {
options.messages['notEqualTo'] = options.message;
}
});
jQuery.validator.addMethod('notEqualTo', function(value, element, param) {
return this.optional(element) || value != $(param).val();
}, '');
</script>
@using (Html.BeginForm())
{
<div>
@Html.LabelFor(x => x.Prop1)
@Html.EditorFor(x => x.Prop1)
@Html.ValidationMessageFor(x => x.Prop1)
</div>
<div>
@Html.LabelFor(x => x.Prop2)
@Html.EditorFor(x => x.Prop2)
@Html.ValidationMessageFor(x => x.Prop2)
</div>
<input type="submit" value="OK" />
}
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