RadAsyncUpload in code behind, how to?

My problem is, nothing happens, the code behind doesn't fire...Maybe someone could point me in the right direction. Is it possible to do something like this or am I totaly wrong here?

default.aspx:

    <telerik:RadProgressManager runat="server" ID="RadProgressManager开发者_Go百科1" />
    <telerik:RadAsyncUpload runat="server" ID="AsyncUpload1" />
    <telerik:RadProgressArea runat="server" ID="RadProgressArea1" />

default.aspx.cs:

    protected void AsyncUpload1_FileUploaded(object sender, FileUploadedEventArgs e)
    {
        const string relativePath = "~/Uploads/";
        var filename = e.File.FileName;
        var parentID = Convert.ToInt32(GridView1.SelectedValue);
        var filesize = Convert.ToInt32(e.File.ContentLength);
        var physicalSavePath = MapPath(relativePath) + filename; 

        //Store file info in database
            var app_FilesAdapter = new app_FilesTableAdapter();
            app_FilesAdapter.Insert(filename, relativePath + filename, parentID, 1, DateTime.Now, filesize);

        //Save physical file on disk
            e.File.SaveAs(physicalSavePath, true);
    }