ASP.NET MVC 3 client-side validation with parameters

Question

Following on from this post Perform client side validation for custom attribute

I am trying to get my head around how to do this, passing additional parameters to the client-side script

As I understand it so far to implement custom validation with MVC 3 the following is required

Create a custom validation attribute

Based on ValidationAttribute and implementing IClientValidatable. I have also see some examples deriving from ModelValidator, which seems to implement the functionality of both ValidationAttribute and IClientValidatable. So this is my first point of confusion as to what the diffirences are or whether ModelValidator was used in MVC 2 but is now deprecated or what ?

An instance of ModelClientValidationRule must be returned from GetClientValidationRules() to specify details such as the error message, ValidationType (which I understand to be the name of the Javascript function that will perform the client-side validation) and any additional custom parameters that the attribute may have, and that need to be passed to the Javascript validation.

I assume that the runtime (not sure which part of it) then use the ModelClientValidationRule to generate html attribute in the tag elements as follows:

data-val="true"  (to indicate that the element requires validation)
data-val-[ValidationType]=[ErrorMessage]
data-val-[ValidationType].[ValidationParameters(n).Key]=[ValidationParameters(n).Value]

Implement the client-side validation logic

A Javascript function must be created and added to jQuery.validators with jQuery.validators.addmethod() so that JQuery is aware of it when it need to be executed. Something like:

jQuery.validator.addMethod(
    'greaterThan', 
    function (value, element, params) {
        /.../
       return /* true or false   */ ; 
    },
    ''
); 

My question here is whether the signature 'function (value, element, params)' is standard for methods that will handle validation and I assume it will be called by some jQuery functionality at the appropriate time such as before a form is submitted or when an element looses fuces or on keyUp events. I just don't undertand how you can controll this i.e. choose which event is appropriete for yout custom validation.

Implement an unobtrusive adapter

This translates unobtrusive attributes to; something I am not very clear on, but assume it to be a jQuery Rule, but I am not clear on how those work. Something like

jQuery.validator.unobtrusive.adapters.add(
    'futuredate', 
    { },
    function (options) {
        options.rules['greaterThan'] = true;
        options.messages['greaterThan'] = options.message;
    }
); 

My question here is about 'function (options)'. Is this the function that will be called before 'function (value, element, params)' and is responsible for extracting the unobtrusive tags into a data structure that can be understood by jQuery.Validation. From the code example it seems to me that options is an object that contains both, the attribute values from the tag (such as options.message) and the jQuery relevant properties it must map to (such as options.messages['ClientSideValidationFunctionName']. If so how are custom parameters retrieved and mapped.

I hope I have not added any additional confusion.

Answer 1

You could use the ValidationParameters property to add custom parameters to the rule:

public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
{
    var rule = new ModelClientValidationRule
    {
        ErrorMessage = this.ErrorMessage,
        ValidationType = "futuredate",
    };
    rule.ValidationParameters.Add("param1", "value1");
    rule.ValidationParameters.Add("param2", "value2");
    yield return rule;
}

which could be used in the adapter:

jQuery.validator.unobtrusive.adapters.add(
    'futuredate', 
    [ 'param1', 'param2' ],
    function (options) {
        var param1 = options.params.param1; // shall equal 'value1'
        var param2 = options.params.param2; // shall equal 'value2'
        // TODO: use those custom parameters to define the client rules
    }
);

---

UPDATE:

As requested in the comments section here's how you could pass those parameters to the custom validator rule function:

jQuery.validator.unobtrusive.adapters.add(
    'futuredate', 
    [ 'param1', 'param2' ],
    function (options) {
        // simply pass the options.params here
        options.rules['greaterThan'] = options.params;
        options.messages['greaterThan'] = options.message;
    }
);

jQuery.validator.addMethod('greaterThan', function (value, element, params) {
    // params here will equal { param1: 'value1', param2: 'value2' }
    return ...
}, '');