MVC: How do I set a C# static variable from within a javascript block?

Question

I have this function that I would like to be able to make changes to a static class.

$("#DDLRegion").change(function () {

     var selectedItem = $(this).val();
     ViewBag.Region = selectedItem;
     @RegionSwitch.setRegion(ViewBag.Region);

     switch (selectedItem) {
        case 'Place':
           window.location.href = '@Url.Action("Index", "Place")'
           break;
        case 'Thing' :
           window.location.href = '@Url.Action("Index", "Thing")'
           break;
        case 'Region' :
           window.location.href = '@Url.Action("Index", "Region")'
           break;
        default:
           window.location.href = '@Url.Action("Index", "Place")'
           alert("Blarg");
           break;
     }
  });

Is there a way to be able to access a C# static class from within (what I believe to be) a jQuery script? I'm new to MVC and web development in general. Any advice is also welcome on becoming a better dev.

@RegionSwitch._currentRegion = selectedItem;

The above does not work either and appears in Chrome's JavaScript console as = selectedItem;

You will need to post to your controller to change the server side variables. Google jQuery post for more info. — Bill Cheng
– Bill Cheng, Commented Apr 28, 2015 at 20:13
You're trying to change a serverside object from the client, that won't work. The client javascript is unaware of any server side objects, so you would have to post your values to the server, for instance using an Ajax call. — Stephen
– Stephen, Commented Apr 28, 2015 at 20:27

Andre Pena · Accepted Answer · 2015-04-28 21:38:19Z

0

As @BillCheng and @Stephen said, what you are trying to do is to do a post request from jQuery.

This is how you implement a post request (Ajax) on jQuery.

On the ASP.NET MVC side, Actions work the same regardless of the input being Ajax or not. You just have to implement your Action parameters in such a way that they will match your post parameters. Here's a good article about model binding.

answered Apr 28, 2015 at 21:38

Andre Pena

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Simon Fletcher Over a year ago

So I threw this here post request at it, but I can't seem to get it to work. Gives a 500 error (super helpful).

$.ajax({             url: '/region/changeRegion',             type: 'POST',             data: selectedItem,             dataType: 'String',             success: function (data) {                alert(data);             },             error: function () {                alert('Nope');             }          });

Simon Fletcher · Accepted Answer · 2015-05-05 20:16:42Z

OK, so I've solved my problem after looking around at POST requests. Thanks @BillCheng, @Stephen and @andrerpena for the advice. I posted my data to a controller which then did all the cool C# things I needed.

Ajax request inside javascript change function

     $.ajax({
        url: '/region/changeRegion',
        type: 'POST',
        data: { "selectedRegion": $(this).val() },
        dataType: 'text',
        success: function (data) {
           alert(data);
        },
        error: function () {
           alert('Nope');
        }
     });

And a controller action to handle the string (js calls it text -_-)

  [HttpPost]
  public void ChangeRegion(string selectedRegion)
  {
     RegionSwitch._currentRegion = selectedRegion;
  }

For anyone running into this problem in the future, the expected parameter name needs to match the one from the ajax request.

data: { "**selectedRegion**" : $(this).val() },
public void ChnageRegion(string **selectedRegion**)

Also don't forget to match up the url to the correct controller and action.

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