In this article I will explain with an example, how to use DropDownList SelectIndexChanged event in ASP.Net MVC.
Note: For beginners in ASP.Net MVC, please refer my article ASP.Net MVC Hello World Tutorial with Sample Program example.
 
 

Model

The Model class consists of the following property.
public class PersonModel
{
    /// <summary>
    /// Gets or sets Gender.
    /// </summary>
    [Display(Name = "Gender:")]
    public string Gender { 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 the Action Method, the values posted from the Form inside the View are received through this parameter.
public class HomeController : Controller
{
    // GET: Home
    public ActionResult Index()
    {
        return View();
    }
 
    [HttpPost]
    public ActionResult Index(PersonModel person)
    {
        string gender = person.Gender;
        return View();
    }
}
 
 

View

HTML Markup

Inside the View, in the very first line the PersonModel class is declared as model for the View.
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 View also consists of an HTML Form which consists of:
Label - Created using Html.LabelFor for displaying text.
The Form consists of an HTML Table which consists DropDownList created using Html.DropDownListFor Helper methods respectively.
Then DropDownList has two ListItem i.e. Male and Female.
Finally, ListItem has been assigned with an onchange event handler, and when the ListItem is click or unclick, a JavaScript function OnGenderChanged submits the Form and in turn calls the Controller’s Action method.
@model DropDownList_OnChange_MVC.Models.PersonModel
@{
     Layout = null;
}
 
<!DOCTYPE html>
 
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title> 
</head>
<body>
    @using (Html.BeginForm("Index", "Home", FormMethod.Post, new { @id = "Form1" }))
    {
        <table cellpadding="0" cellspacing="0">
            <tr>
                <td>@Html.LabelFor(m => m.Gender)</td>
                <td>
                    @Html.DropDownListFor(m => m.Gender, new List<SelectListItem>
                   { new SelectListItem{Text= "Male", Value= "M"},
                     new SelectListItem{Text= "Female", Value= "F"}}, "Please select", new  { @onchange = "OnGenderChanged()" })
                </td>
            </tr>
        </table>
    }
    <script>
        function OnGenderChanged() {
            document.getElementById("Form1").submit();
        };
    </script>
</body>
</html>
 
 

Screenshots

The Form

DropDownList SelectedIndexChanged event in ASP.Net MVC
 

Values captured in Controller when Form is submitted

DropDownList SelectedIndexChanged event in ASP.Net MVC
 
 

Downloads

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