In this article I will explain with an example, how to implement Server Side validation of CheckBox in ASP.Net MVC Razor.
The Server Side validation will be performed for CheckBox using Model and Data Annotations in ASP.Net MVC Razor.
 
 
Custom Validation Data Annotations Attribute for CheckBox
The Required Data Annotation attribute does not work for Boolean validation i.e. performing validation Checked or Unchecked for a CheckBox.
Hence a new class will be created for developing Custom Validation Data Annotations Attribute for CheckBox. This attribute will validate the CheckBox as Boolean validation i.e. only two values True or False and will raise error when the value is False.
using System.ComponentModel.DataAnnotations;
 
public class CheckBoxRequired : ValidationAttribute
{
    public override bool IsValid(object value)
    {
        if (value is bool)
        {
            return (bool)value;
        }
 
        return false;
    }
}
 
 
Model
The following Model class consists of one property TermsConditions to which the CheckBoxRequired Custom Data Annotation attribute has been applied.
The Data Annotations attributes can be used with the Entity Data Model (EDM), LINQ to SQL, and other data models.
The CheckBoxRequired Custom Data Annotation has been specified with a property Error Message with a string value. As the name suggests, this string value will be displayed to the user when the validation fails.
using System.ComponentModel.DataAnnotations;
 
namespace CheckBox_Validation_ServerSide_MVC.Models
{
    public class PersonModel
    {
        [Display(Name = "I accept the above terms and conditions.")]
        [CheckBoxRequired(ErrorMessage = "Please accept the terms and condition.")]
        public bool TermsConditions { get; set; }
    }
}
 
 
Controller
The Controller consists of following two Action methods.
Action method for handling GET operation
Inside this Action method, simply the View is returned.
 
Action method for handling POST operation
This Action method handles the POST operation and when the form is submitted, the object of the PersonModel class is sent to this method.
The state of the submitted Model is checked using ModelState.IsValid property.
Note: ModelState.IsValid property is an inbuilt property which verifies two things:
1. Whether the Form values are bound to the Model.
2. All the validations specified inside Model class using Data annotations have been passed.
 
public class HomeController : Controller
{
    // GET: Home
    public ActionResult Index()
    {
        return View();
    }
 
    [HttpPost]
    public ActionResult Index(PersonModel person)
    {
        if (ModelState.IsValid)
        {
            // Validation success.
        }
 
        return View();
    }
}
 
 
View
Inside the View, in the very first line the PersonModel class is declared as Model for the View.
 
The Form
The View consists of an HTML Form which has been created using the Html.BeginForm method with the following parameters.
ActionName – Name of the Action. In this case the name is Index.
ControllerName – Name of the Controller. In this case the name is Home.
FormMethod – It specifies the Form Method i.e. GET or POST. In this case it will be set to POST.
 
The Form consists of the following there HTML Helper functions:-
1. Html.CheckBoxFor – Creating a CheckBox for the Model property.
2. Html.LabelFor – Displaying the Model property name.
3. Html.ValidationMessageFor – Displaying the Validation message for the property.
There is also Submit button which when clicked, the Form gets submitted.
@model CheckBox_Validation_ServerSide_MVC.Models.PersonModel
 
@{
    Layout = null;
}
 
<!DOCTYPE html>
 
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
    <style type="text/css">
        body { font-family: Arial; font-size: 10pt; }
        .error { color: red; }
    </style>
</head>
<body>
    @using (Html.BeginForm("Index", "Home", FormMethod.Post))
    {
        <table>
            <tr>
                <td>@Html.CheckBoxFor(m => m.TermsConditions)</td>
                <td>@Html.LabelFor(m => m.TermsConditions)</td>
            </tr>
            <tr>
                <td></td>
                <td>
                    @Html.ValidationMessageFor(m => m.TermsConditions, "", new { @class = "error" })
                </td>
            </tr>
            <tr>
                <td></td>
                <td><input type="submit" value="Submit" /></td>
            </tr>
        </table>
    }
</body>
</html>
 
 
Screenshot
Server Side CheckBox validation in ASP.Net MVC Razor
 
 
Downloads
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