In this article I will explain with an example, how to implement CheckBox check changed event in ASP.Net Core (.Net Core 8) MVC.
Note: For beginners in ASP.Net Core (.Net Core 8) MVC, please refer my article ASP.Net Core 8: Hello World Tutorial with Sample Program example.
 
 

Model

The Model class consists of the following property.
public class PersonModel
{
    [Display(Name = "Do you have Passport?")]
    public bool HasPassport { get; set; }
}
 
 

Controller

The Controller consists of following Action methods.

Action method for handling GET operation

Inside this Action method, simply the View is returned.
 

Action method for handling POST operation

Inside this Action method, the HasPassport property is verified and based on whether CheckBox is checked or unchecked, its value is true or false respectively.
public class HomeController : Controller
{
    // GET: Home
    public IActionResult Index()
    {
        return View();
    }
 
    [HttpPost]
    public IActionResult Index(PersonModel person)
    {
        if (person.HasPassport)
        {
 
        }
 
        return View();
    }
}
 
 

View

HTML Markup

Inside the View, in the very first line the PersonModel class is declared as model for the View and ASP.Net TagHelpers is inherited.
The View consists of an HTML Form which has been created using the following TagHelpers 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 also consists of a HTML Table, which consists of Input CheckBox, and Label.
The Input CheckBox has been assigned with asp-for Tag Helper attribute and its value is set with the HasPassport property. Thus, this signifies that the validation will be performed for the HasPassport property.
Then Label has been assigned with asp-for Tag Helper attribute and here also its value is set with the HasPassport property which signifies that it is used for displaying the Model property name.
Finally, CheckBox has been assigned with an onchange event handler, and when the CheckBox is checked or unchecked, a JavaScript function OnPassportChanged submits the Form and in turn calls the Controller’s Action method.
@model CheckBox_Changed_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>
</head>
<body>
    <form asp-action="Index" asp-controller="Home" method="post" id="Form1">
        <table>
            <tr>
                <td><input asp-for="HasPassport" type="checkbox" onchange="OnPassportChanged()" /></td>
                <td><label asp-for="HasPassport"></label></td>
            </tr>
        </table>
    </form>
    <script>
        function OnPassportChanged() {
            document.getElementById("Form1").submit();
        };
    </script>
</body>
</html>
 
 

Screenshots

The Form

CheckBox Check Changed event in ASP.Net Core
 

Values captured in Controller when Form is submitted

CheckBox Check Changed event in ASP.Net Core
 

Values captured in Controller when Form is unchecked

CheckBox Check Changed event in ASP.Net Core
 
 

Downloads

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