To pass select values to a POST request in ASP.NET MVC, you can use a form or AJAX to send the data to the server. Here’s an example of how you can accomplish this:

1. Create a form in your view: Add a form element to your view that contains the select element(s) with the desired values.

<form method="post" action="/ControllerName/ActionName">
    <select name="selectedValue">
        <option value="value1">Value 1</option>
        <option value="value2">Value 2</option>
        <option value="value3">Value 3</option>
    </select>
    <button type="submit">Submit</button>
</form>

In the above example, the select element contains multiple option elements with different values. The form has a submit button that triggers the POST request.

2. Handle the POST request in your controller: In your controller, create an action method that corresponds to the form’s action attribute. The action method should have the [HttpPost] attribute to handle the POST request.

[HttpPost]
public ActionResult ActionName(string selectedValue)
{
    // Use the selectedValue in your logic
    // ...

    return RedirectToAction("Result");
}

In the above example, the action method receives the selectedValue as a parameter. You can use this value in your logic as needed. After processing the data, you can redirect the user to a result page or perform any other action.

3. Validate and process the data: Inside the action method, you can validate and process the received data according to your requirements.

Note: Make sure that the name attribute of the select element in the form matches the parameter name in the action method signature. In this example, both are named “selectedValue”.

This approach submits the form and sends the selected value(s) as form data in the body of the POST request. When the form is submitted, the browser navigates to the specified URL, and the server-side code in the action method is executed.

Alternatively, if you want to send the data asynchronously without a page refresh, you can use AJAX to make the POST request. This allows you to handle the response on the client-side without navigating away from the current page.