添加模型错误MVC后，如何使验证消息消失？

Question

In my view I have a check box and a text box if the check box is checked then I require the text box to be filled with some text. To do this I call

ModelState.AddModelError("item", "Please enter some text.");

only if the checkbox returns true and the text box isempty when my page re-displays I receive the proper message where I have

@Html.ValidationMessageFor(model => model.item)

but I would like the text to go away after a use types something in the text box, without the user having to hit submit like it does with data annotation. How can I fix this?

I'm using c# Asp.net 4 with entity framework 5

Answer 1

ModelState.AddModelError is server-side validation, so the error message will not go away until you post to the server.

If you want the functionality you describe, you can define a custom validation attribute and apply it both client side and server-side. For example, you can define a "RequiredIf" custom validation attribute, which would make a field required if a certain other condition is met (in this case, if another property is true):

public class RequiredIfAttribute : RequiredAttribute
    {
        private String PropertyName { get; set; }
        private Object DesiredValue { get; set; }

        public RequiredIfAttribute(String propertyName, Object desiredvalue)
        {
            PropertyName = propertyName;
            DesiredValue = desiredvalue;
        }

        protected override ValidationResult IsValid(object value, ValidationContext context)
        {
            Object instance = context.ObjectInstance;
            Type type = instance.GetType();
            Object proprtyvalue = type.GetProperty(PropertyName).GetValue(instance, null);
            if (proprtyvalue.ToString() == DesiredValue.ToString())
            {
                 ValidationResult result = base.IsValid(value, context);
                return result;
            }
            return ValidationResult.Success;
        }
    }

Register it in your global.asax:

DataAnnotationsModelValidatorProvider.RegisterAdapter(typeof(RequiredIfAttribute),typeof(RequiredAttributeAdapter);

Then you can use it like this:

public class YourModel {
    // This is the property tied to your checkbox
    public bool YourBooleanProperty { get; set; }

    [RequiredIf("YourBooleanProperty", true)]
    public string Item { get; set; }
}

You could also leverage the JQuery Validate plugin to perform the same conditional validation client-side.

Answer 2

尝试使用jquery，将eventListener附加到该字段，并删除MVC添加到该字段的类CSS并隐藏验证标签