Validation Context is always NULL?

问题

I have custom validation attribute such as this:

    public class MyCustomAttribute : ValidationAttribute {
    protected override ValidationResult IsValid(object value, ValidationContext validationContext) {
        if ((int)value == 100) {
            // do some checking to validate & return ValidationResult accordingly

        } else return ValidationResult.Success;
    }
}

In usage like this:

    [DisplayName("My Custom Property")]
    [MyCustom(ErrorMessage = "ERROR!!!")]
    public int? MyCustomProperty { get; set; }

My question is: why is it that inside MyCustomAttribute, within the IsValid method, validationContext is always NULL? Is there anything special I need to set to get it not to be NULL?

回答1:

if you use

ValidationResult IsValid(object value, ValidationContext validationContext)

to check if data is valid you have to use

v.GetValidationResult(propertyValue,new ValidationContext(this))!= ValidationResult.Success

instead of

 v.IsValid(propertyValue)

来源：https://stackoverflow.com/questions/5408658/validation-context-is-always-null