How to add the UserId parameter to the query string of a XmlUrlDataSource in SharePoint? -

I have an ASPX that returns XML data using query string parameter UserId. It should be UserId SharePoint current user.

I create the data source and drag it to the page, but I do not know how to add the parameter to the data source so that it can send the current user id. I tried to add the parameter to the datasource parameter grid but when ASPX is always called it, it always uses the default value and not the current user id

You should be able to do this by adding a parameter through the context menu of the control menu (like DataFormWebPart).