updating aspx page from server

Question

Currently I am working on a project where a web page will start a 3 hour data transfer process through the use of a web service. Basically a list of Id's are used to tell the web service to transfer an data object from one database to another.

When I start the process, I would like to allow the user to remain in control. He must be able to see how far the current process is, and be able press a cancel button to stop the data transfer. All this is run from an ASPX web page.

I have discovered that trying to run the process asynchronous does not allow me to update the user interface as I had hoped. Only when the entire process is finished Another problem I might face is that since the process takes a lot of time, the server objects might get refreshed at some point, which could cause me to lose my progress.

I am currently at the point where I am deciding whether or not to use the web server to process the data transfer. If I am, my current solution is to use tasks to run the process asynchronously, and use client side web calls (to the aspx page) to update the client interface. I am also implementing the IRegisteredObject interface for my work object. IRegisteredObject explanation

Any idea on how to best tackle this problem is most welcome. I really want to know if I'm heading in the right direction.

Answer 1

My suggestion would be for you to create a WCF service, which is not hosted within ASP.NET and to make your ASP.NET application call that service to trigger the long running job that performs the data transfer. Meanwhile your ASP.NET app notifies the user that it has triggered the job and you can expose other endpoints on your service which the ASP.NET application can query through a user request in order to extract and report progress.

Answer 2

The web server will only run one page at a time for each user, so if you want to communicate with the browser while the process is running, you can't run the progress from a request. You need to start it as an independent background thread, so that you can finish the request that started the process.

After that you can send requests to the server either to do polling for status of the process, or to control the process.

If possible you should run the process entirely outside of IIS, for example as a console application. That way you only have to keep track of the fact that there is a process running in the web application, for example putting that in a database so that it survives IIS recycling.