How to update a page from a worker thread

Question

Hi

I have a ASPX page which queries from a database. Once we have the dataset it is bound to a gridview and displayed on the page. All this happens in the Page_Load event.

Ofcourse this a simplistic approach. What is the best way to inform the user that data is being retrieved and when we have the data to update the page with the results in the dataset.

I want all this to happen within the same ASPX page and do not want to hop around pages to achieve this. I looked at update panels however it wasn't clear to me how this could be done with an update panel without having a control which triggers the update for the update panel. There are no controls on my page whhich initiate the database query, it occurs as the page is loaded.

If I do the query in a worker thread and then call the Update method on a UpdatePanel with the gridview as part of it, it doesn't work. Nothing happens.

Any thoughts or help? Thanks.

Answer 1

Well, this is a good question. Personally I have two pretty similar methods to do this:

1. Have a java script that will make an UpdatePanel reload with a short interval. This will create a series of post-backs to the server. During each post-back you should chek you worker thread and return immediately with the state report, usually one of error, pending, success + data
2. With a java script, make an asynchronous request to a web-service that will block until the data is fetched. This method brings no latency as compared to the previous one (the time between polls), but may suffer from some browsers/servers attitude to hanging open connections. This is normally solved by some interval (say, 1 minute) introduced, so that the hanging request will return with a message like need more time, in which case the java script should simply repeat the request.