From here: c# - Unable to pass more than 1 parameter using @Url.Action - Stack Overflow

Now the second parameter is passed in!!

$("#filesTemplate").kendoUpload({
	async: {
        autoUpload: false,
        saveUrl: "@Html.Raw(@Url.Action("Attachments_Save", "Upload", new { parentId, baseTableName }))",
        removeUrl: "@Url.Action("Attachments_Delete", "Upload")"
     }
});