In this article I will explain with an example, how to implement Server Side validation of RadioButton in ASP.Net Core MVC.
The Server Side validation will be performed for RadioButton using Model and Data Annotations in ASP.Net Core MVC.
 
 
Model
The following Model class consists of one property Gender. The property is decorated with the following Data Annotation attributes for performing validations.
1. Required Data Annotation attribute.
The Data Annotations attributes can be used with the Entity Data Model (EDM), LINQ to SQL, and other data models.
The Required 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 RadioButton_Validation_ServerSide_MVC_Core.Models
{
    public class PersonModel
    {
        [Required(ErrorMessage = "Gender is required.")]
        public string Gender { 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.
public class HomeController : Controller
{
    public IActionResult Index()
    {
        return View();
    }
 
    [HttpPost]
    public IActionResult Index(PersonModel person)
    {
        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 following ASP.Net Tag Helpers attributes.
asp-action – Name of the Action. In this case the name is Index.
asp-controller – Name of the Controller. In this case the name is Home.
method – It specifies the Form Method i.e. GET or POST. In this case it will be set to POST.
The Form consists of HTML Input RadioButtons, HTML Label for displaying the text for each RadioButtons, a SPAN and a Submit Button.
The Input RadioButtons has been assigned with asp-for Tag Helper attribute and its value is set with the Gender property. Thus, this signifies that the validation will be performed for the Gender property.
The SPAN has been assigned with asp-validation-for Tag Helper attribute and here also its value is set with the Gender property which signifies that it is used for displaying the Validation message for the Gender property.
When the Submit button is clicked, the Form gets submitted and the Gender value is sent to the Controller.
@model RadioButton_Validation_ServerSide_MVC_Core.Models.PersonModel
@addTagHelper*, Microsoft.AspNetCore.Mvc.TagHelpers
@{
    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>
    <form method="post" asp-controller="Home" asp-action="Index">
        <table>
            <tr>
                <td>
                    <label>Male</label>
                    <input type="radio" asp-for="Gender" value="M" />
                    <label>Female</label>
                    <input type="radio" asp-for="Gender" value="F" />
                </td>
                <td><span asp-validation-for="Gender" class="error"></span></td>
            </tr>
            <tr>
                <td><input type="submit" value="Submit" /></td>
                <td></td>
            </tr>
        </table>
    </form>
</body>
</html>
 
 
Screenshot
Server Side RadioButton validation in ASP.Net Core
 
 
Downloads
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