Send Selected DropDownList value to HomeController ActionResult

Question

Hi I have a drop down list that is filled in from comma delimited values in the config. This works fine.

What I am trying to do is to send the selected value on button click to a ActionResult in the HomeController.

I created a Model, which is taking a string. When I hit the button I get error:

The view 'TestAction' or its master was not found or no view engine supports the searched locations.

This is what my Controller looks like:

    [HttpPost]
    [ActionName("TestAction")]
    public ActionResult TestAction(SQL_Blocks_App.Models.DropdownList SelectedValue)
    {

        //System.Diagnostics.Debug.WriteLine(SelectedValue);



        return View();
    }

This is what my model looks like:

public class DropdownList
{
    //
    // GET: /DropdownList/
    [Display(Name = "Servers")]
    public string SelectedValue{ get; set; }



}

and this is what my Index View looks like:

    <form id="SelectedValue" action="/Home/TestAction" method="post" style="margin: 0">
       <div class="col-lg-5">
            @{
            ViewBag.Title = "Index";
            }
            @Html.DropDownList("YourElementName", (IEnumerable<SelectListItem>)ViewBag.DropdownVals, "--Choose Your Value--", new

            {

               //size = "5",
               style = "width: 600px"

            })


        </div>
        <div class="col-lg-5">
            <input type="submit" value="Run Query" />

            <input id="Button2" type="button" value="Clear" onclick="window.location.reload()" />

        </div>
    </form>

I want to clarify. My end goal is to use the selected value in a SQL query in the ActionResult and return the results back to the index so I can fill them in a table. ( You don't have to show me how to do the SQL part for now I just would like to see the selected value at least printed in the output.)

Answer 1

The default framework behavior of return View() is to return a view with the same name as the currently-executing action. Which is TestAction. The error is telling you that no such view was found.

You have a couple of options. You can either create the view, or you can return something else. For example, if you want to redirect back to the Index then you can return a redirect result:

return RedirectToAction("Index");

You could also specify the Index view in the response:

return View("Index");

However, keep in mind that the URL will still be for TestAction and not for Index, which could result in unexpected changes to behavior if you're not aware of this.

---

Edit: Based on comments on this answer, it sounds like what you actually want is to build a pair of actions which generally operate on the same view. This isn't particularly common for an index view, but is very common for edit views. The only difference is semantics, structurally the concept works anywhere.

Consider two actions:

public ActionResult Index()
{
    // just show the page
    return View();
}

[HttpPost]
public ActionResult Index(SQL_Blocks_App.Models.DropdownList SelectedValue)
{
    // receive data from the page
    // perform some operation
    // and show the page again
    return View();
}

Requests between these two actions would differ only by the HTTP verb (GET or POST), not by the action name on the URL. That name would always be "Index". But when the form on the index view is submitted via POST and has a "SelectedValue", the second action is invoked instead of the first.

In that second action you would perform your database interaction, gather whatever data you needed, and if necessary include a model or some additional data in the response.