Don't understand the mechanics of writing own validation attribute
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07-07-2021 - |
Frage
I have written an attribute before, but I I have not written a validation attribute before. I am seriously confused about how it all works together. I have read most of the tutorials online about how to go about accomplishing this. But I am left with a couple of questions to ponder.
Keep in mind that I am trying to write a requiredIf attribute that will only call a remote function if a certain Jquery variable is set... which incidentally is a variable that is pulled from view state... I guess I could make that part of my view model. But I digress
1) The C# code is slightly confusing. I know my attribute should extend the ValidationAttribute, IClientValidatable class and interface respectively. But I am a little confused about what each of the overidden methods should be doing? I am trying to write a requiredIf, how does overwriting these methods help me accomplish this goal?
2) If the variable is not there, I simply don't want the remote function to attempt to validate the field. I don't want any message to pop up on my form. Alot of the tutorials seem to revolve around that.
3) I am confused about what I need to do with the jquery to add this function to the view... What do I need to add to the JQuery to get this thing to work... It seems like a lot of extra coding when I could simply just type up a jquery function that did the same thing with just the same ore less coding... I know it also adds server side validation which is good. But still...
Here is what I have for my jquery side of this equation...
(function ($) {
$validator.unobtrusive.adapters.addSingleVal("requiredifattribute", "Dependent");
$validator.addMethod("requiredifattribute", function (value, element, params) {
if (!this.optional(element)) {
var otherProp = $('#' + params)
return (otherProp.val() != value);
}
return true;
})
}(jQuery));
Here is my Attribute (which is basically carbon copied out of one the required if tutorials... I know I need to customize it more, but once I get a better idea of what every piece is doing I will do that...
[AttributeUsage(AttributeTargets.Property)]
public class RequiredIfAttribute : ValidationAttribute, IClientValidatable {
private const string errorMessage = "The {0} is required.";
//public string
private RequiredAttribute innerAttribute = new RequiredAttribute();
public string DependentProperty { get; set; }
public object TargetValue { get; set; }
public RequiredIfAttribute(string dependentProperty, object targetValue){
this.DependentProperty = dependentProperty;
this.TargetValue = targetValue;
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext) {
var field = validationContext.ObjectInstance.GetType().GetProperty(DependentProperty);
if (field != null) {
var dependentValue = field.GetValue(validationContext.ObjectInstance, null);
if ((dependentValue == null && TargetValue == null) || (dependentValue.Equals(TargetValue))) {
if (!innerAttribute.IsValid(value))
return new ValidationResult(ErrorMessage);
}
}
return ValidationResult.Success;
}
public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context) {
ModelClientValidationRule modelClientValidationRule = new ModelClientValidationRule {
ErrorMessage = FormatErrorMessage(metadata.DisplayName),
ValidationType = "requiredifattribute"
};
modelClientValidationRule.ValidationParameters.Add("dependent", DependentProperty);
yield return modelClientValidationRule;
}
}
UPDATE: What I have simply isn't working
Here is how a property in my model is anotated with the above attribute
[RequiredIf("isFlagSet", true)]
[Remote("ValidateHosFin", "EditEncounter", AdditionalFields = "hospitalFin, encflag", ErrorMessage = "Got Damn this is complex!")]
[MinLength(6)]
public string HostpitalFinNumber { get; set; }
The value in my view that I was trying to key this validation on is set up like so...
ViewData["ADDENCOREDITTEMP"] = encflag;
if (encflag == "AddEnc"){
isFlagSet = true;
}
I embed it into my page like so...
@Html.Hidden("isFlagSet", isFlagSet, new { id = "isFlagSet"})
I can't get my form to submit... The person who said he just tried this and got it to work, could you post the code?
Lösung
Model:
public class X
{
[RequiredIf("y", "y", ErrorMessage = "y is not y")]
public string x { get; set; }
public string y { get; set; }
}
View:
@using(Html.BeginForm())
{
@Html.ValidationSummary()
@Html.TextBoxFor(m => m.x)
@Html.TextBoxFor(m => m.y)
<input type="submit"/>
}
I assume your validation fails on the server side? do you have isFlagSet
property in your view model?