How to use PageAsyncTask with WebRequest for multiple requests? - asp.net

Question

I'm targeting a web service that takes a single string parameter.
On a schedule I want to fire off approximately 100 calls to that web service for 100 values from my database.
To optimise the process I believe I need to do the WebRequest calls asynchronously.
I've come across the code example below on a variety of blogs etc. but can't figure out how to adapt it for my requirement.
How can I wrap up the RegisterAsyncTask inside a foreach loop, parsing through the uri for the WebRequest.Create() that's inside BeginAsyncOperation?
using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Net;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
public partial class AsyncPageTask : System.Web.UI.Page
{
private WebRequest _request;
protected void Page_Load(object sender, EventArgs e)
{
PageAsyncTask task = new PageAsyncTask(
new BeginEventHandler(BeginAsyncOperation),
new EndEventHandler(EndAsyncOperation),
new EndEventHandler(TimeoutAsyncOperation),
null
);
RegisterAsyncTask(task);
}
IAsyncResult BeginAsyncOperation(object sender, EventArgs e,
AsyncCallback cb, object state)
{
_request = WebRequest.Create("http://msdn.microsoft.com");
return _request.BeginGetResponse(cb, state);
}
void EndAsyncOperation(IAsyncResult ar)
{
string text;
using (WebResponse response = _request.EndGetResponse(ar))
{
using (StreamReader reader =
new StreamReader(response.GetResponseStream()))
{
text = reader.ReadToEnd();
}
}
Output.Text = text;
}
void TimeoutAsyncOperation(IAsyncResult ar)
{
Output.Text = "Data temporarily unavailable";
}
}
My intention is to write the response string back into a database. Appreciate this is an additional question but, is there any reason not to include the insert method call within the EndAsyncOperation method ?
This Q&A hints towards my main question but which 4th argument?

Answer 1

First you need to add this to your Web.config file (default is just 2):
<configuration>
<system.net>
<connectionManagement>
<add address="*" maxconnection="100" />
</connectionManagement>
<system.net>
<configuration>
Then you need to add async directive to your page: <%# Page Async="true" %>
protected void Page_Load(object sender, EventArgs e)
{
//...first get UriStringArray from db, and then:
foreach(string uri in UriStringArray)
{
var task = new PageAsyncTask(
new BeginEventHandler(BeginAsyncOperation),
new EndEventHandler(EndAsyncOperation),
new EndEventHandler(TimeoutAsyncOperation),
uri,
true; //run in parallel
);
RegisterAsyncTask(task);
}
}
IAsyncResult BeginAsyncOperation(object sender, EventArgs e, AsyncCallback cb, object state)
{
var request = (HttpWebRequest)WebRequest.Create((string)state);
return request.BeginGetResponse(cb, request);
}
void EndAsyncOperation(IAsyncResult ar)
{
string text;
var request = (HttpWebRequest)ar.State;
using(WebResponse response = request.EndGetResponse(ar))
{
using(StreamReader reader = new StreamReader(response.GetResponseStream()))
text = reader.ReadToEnd();
}
//yes, you can insert in db here, even as a new PageAsyncTask - but then must call ExecuteRegisteredAsyncTasks() manually...
}