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I have a process, that outputs step by step messages (i.e., Processing item 1... Error in item 2 etc etc).
I want this to be output to the user during the process, and not at the end.
I'm pretty sure I need to do this with threading, but can't find a decent example.
933
It's not a threading issue, but a web browser UI issue. You want the browser to render the status as you are doing work on the server. In theory you could do something like:
Response.Write("something");
Response.Flush();
but the Flush() won't ensure the browser actually renders your code at that moment. In reality you cannot control how data is cached/chunked/buffered underway from the server to the browser. So each update should be a 'full' http transaction.
One way, and common one, is to use AJAX to achieve this. The user clicks a button which starts some background work, and you have a javascript timer which polls (makes requests) to check the status of the work, and updates the client browser.
Check out Real-Time Progress Bar With ASP.NET AJAX for doing an ajax progress indicator with ajax and .net.
There's an excellent example of creating a progress bar with a http handler in this article: http://www.asp101.com/articles/matt/progressbar/default.asp
To prove my point, the following code works in Firefox, but not in IE or Chrome:
protected void Page_Load(object sender, EventArgs e)
{
Response.Buffer = false;
Response.Clear();
Response.Write("<html><body>");
Response.Write("1\n");
Response.Flush();
Thread.Sleep(2000);
Response.Write("1\n");
Response.Flush();
Thread.Sleep(2000);
Response.Write("1\n");
Response.Flush();
Thread.Sleep(2000);
Response.Write("1\n");
Response.Flush();
Response.Write("</body></html>");
Response.End();
}
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