Problem sending parameter to my controller using AJAX/JQuery in ASP.Net Core

Question

Any help with this would be much appreciated. I've got a datagrid and a download button on my UI. When the user selects a row in the grid and clicks download, it should pass the int id as parameter to my Download method on my controller, which triggers further processing.

I have tried using Ajax/JQuery for this, but alas I'm a novice and I keep getting 0 passed to controller. It is correctly selecting my id, as I have an alert which displays the correct id with each selection. I get no errors upon inspection in Chrome.

Please see relevant code below:

//html

            <form asp-controller="Home" asp-action="Download" method="get">
                <div id="downloadButton"></div>
            </form>

//JQuery datagrid on my view:

    $("#gridContainer2").dxDataGrid({
        dataSource: DevExpress.data.AspNet.createStore({
            loadUrl: url + "/GetLoadHistory",
            key: "loadId"

        }),
        selection: {
            mode: "single"
        },
        hoverStateEnabled: true,
        paging: {
            pageSize: 10
        },

        editing: {
            mode: 'row',

        },
        onSelectionChanged: getLoadId
    });

//JQuery functions with Ajax:

function getLoadId() {
    var dataGrid = $("#gridContainer2").dxDataGrid("instance");
    var loadId = dataGrid.getSelectedRowKeys();
    console.log("Load ID: " + loadId);
    download(loadId);

}

function download(loadId) {

    $("#downloadButton").dxButton({
        text: "Download Selected",
        type: "normal",
        icon: "/favicon.ico",
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        useSubmitBehavior: true,
        onClick: function (e) {
            $.ajax({
                url: 'https://localhost:44346/home/Download/',
                data: { LoadID: loadId}
        }).done(function () {
                DevExpress.ui.notify("Downloading results for Load ID: " + loadId, "info", 1500);
            });

        }

    });
};

//download method on home controller:

   [HttpGet]
    public async Task<IActionResult> Download(int loadId)
    {
        //always 0...
        Console.WriteLine("Load ID passed from UI:" + loadId); 
        //further processing
    }

Answer 1

Try changing your jQuery.ajax to the following:

$.ajax({
 url: 'https://localhost:44346/home/Download/',
 type: 'GET',
 data: {
  loadId: getLoadId()
 }
}).done(function() {
 DevExpress.ui.notify("Downloading results for Load ID: " + loadId, "info", 1500);
});

Note I've lowercased loadId in the data you're sending to the server and explicitly stated that this is a HTTP GET request.

Edit: you weren't calling the getLoadId function at all; the important line here is loadID: getLoadId(). Confirm this by setting a breakpoint in getLoadId in your browsers developer tools - I'm pretty sure without the above change that breakpoint won't be hit when you click your button.