How Can I Add Attributes To Model Class Based On Some Conditions

Question

5.00/5 (1 vote)

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Dear All,

I want to add attributes to model class properties based on some conditions

example:

Suppose the following EmployeeModel Class:

C#

public class EmployeeModel
    {
        public int EmployeeId { get; set; }

        [Required]
        public string EmployeeName { get; set; }
 
    }

I want to add the Required attribute on EmployeeName Based on Some Condition.

How can i implement that?

Posted 12-Dec-15 20:51pm

_ProgProg_

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Rajdeep Debnath · Accepted Answer · 2015-12-12T21:52:00

Solution 1

Here is the updated code

Class file

C#

public class ConditionalRequired : ValidationAttribute, IClientValidatable
    {
        public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
        {
            var mcvrTwo = new ModelClientValidationRule();
            mcvrTwo.ValidationType = "contactnovalid";
            mcvrTwo.ErrorMessage = "Contact No is not valid.";
            mcvrTwo.ValidationParameters.Add
            ("contactnoregex", @"\b\d{10}\b");
            return new List<ModelClientValidationRule> { mcvrTwo };
        }

        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            var obj = validationContext.ObjectInstance as Customer;
            if (obj.CustomerID == 1)
            {
                return ValidationResult.Success;
            }
            return new ValidationResult("Contact No is not valid");
        }
    }

CSHTML file

JavaScript

<script src="~/Scripts/jquery-1.10.2.js"></script>
<script src="~/Scripts/jquery.validate.min.js"></script>
<script src="~/Scripts/jquery.validate.unobtrusive.min.js"></script>
<script src="~/Scripts/MicrosoftAjax.js"></script>

<script type="text/javascript">
    $.validator.addMethod("contactnovalid", function (value, element, contactnoregex) {
        var patt = new RegExp(contactnoregex);
        if (patt.test(value))
            return true;
        return false;
    });
    $.validator.unobtrusive.adapters.add("contactnovalid", ["contactnoregex"], function (options) {
        options.rules["contactnovalid"] = options.params.contactnoregex;
        options.messages["contactnovalid"] = options.message;
    });
</script>

Posted 12-Dec-15 21:52pm

Rajdeep Debnath

Updated 13-Dec-15 4:04am

v3

Comments

_ProgProg_ 13-Dec-15 4:16am

Can you give me more details of how to use this?

Rajdeep Debnath 13-Dec-15 4:34am

Yes, can you let me know the condition also? Will it check other model property?

the steps are
1. Create a new class and derive the class from ValidationAttribute class (or add the above code). This will create custom attribute.
2. The IsValid method will return true or false based on EmployeeName value entered by the user/system, but here logic can vary based on your condition
3. Apply the attribute on your model property

_ProgProg_ 13-Dec-15 4:56am

Actually it did the purpose but the code is implemented after post action and i want that code run on rendering view.

Rajdeep Debnath 13-Dec-15 5:06am

Can you provide me bit more detail....about rendering view part

_ProgProg_ 13-Dec-15 5:20am

It's a simple Create view with property EmployeeName.
For testing now i am using ConditionalRequired with always return false;
Here is My Code:
if (ModelState.IsValid)
{
//Some Code For Insert
//Some Code For Redirect
}
else
return View();

As You Can See, Now i added Else Statement to return to the same view and view the message that employee name is not valid.
So this is not occured until i press the Create button.

Rajdeep Debnath 13-Dec-15 5:48am

Please check if the below code works.....

From ValidationContext you will get the object instance and run conditional logic on other property of the object

public class ConditionalRequired : ValidationAttribute
{
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
var obj = validationContext.ObjectInstance as Customer;
if (obj.CustomerID == 0)
{
return ValidationResult.Success;
}
return new ValidationResult("Contact No is not valid");
}
}

_ProgProg_ 13-Dec-15 6:31am

Actually Rajdeep it gives me the same result.
The problem is that validation occurs after the Post Action not before.
[for example] If i added a required attribute on the employeeName property directly, then i pressed on the Post Action [Create Button] then validation occurs on client side.
But after implementing [ConditionalRequired], My condition is validated on server as it depends on the property value.

Rajdeep Debnath 13-Dec-15 8:45am

You can try the below...where they implemented IClientValidatable to the ConditionalRequired class

https://thewayofcode.wordpress.com/tag/custom-unobtrusive-validation/

or you can use Jquery to validate....

_ProgProg_ 16-Dec-15 1:08am

Thanks Rajdeep,
That was very helpful.