My plan is to have a user write down a movie title in my program and my program will pull the appropiate information asynchronously so the UI doesn't freeze up.
Here's the code:
public class IMDB
{
WebClient WebClientX = new WebClient();
byte[] Buffer = null;
public string[] SearchForMovie(string SearchParameter)
{
//Format the search parameter so it forms a valid IMDB *SEARCH* url.
//From within the search website we're going to pull the actual movie
//link.
string sitesearchURL = FindURL(SearchParameter);
//Have a method download asynchronously the ENTIRE source code of the
//IMDB *search* website.
Buf开发者_如何学Cfer = WebClientX.DownloadDataAsync(sitesearchURL);
//Pass the IMDB source code to method findInformation().
//string [] lol = findInformation();
//????
//Profit.
string[] lol = null;
return lol;
}
My actual problem lies in the WebClientX.DownloadDataAsync() method. I can't use a string URL for it. How can I use that built in function to download the bytes of the site (for later use I will convert this to string, I know how to do this) and without freezing up my GUI?
Perhaps a clear cut example of the DownloadDataAsync so I can learn how to use it?
Thanks SO, you're always such a great resource.
There is a newer DownloadDataTaskAsync method that allows you to await the result. It is simpler to read and easier to wire up by far. I'd use that...
var client = new WebClient();
var data = await client.DownloadDataTaskAsync(new Uri(imageUrl));
await outstream.WriteAsync(data, 0, data.Length);
You need to handle the DownloadDataCompleted
event:
static void Main()
{
string url = "http://google.com";
WebClient client = new WebClient();
client.DownloadDataCompleted += DownloadDataCompleted;
client.DownloadDataAsync(new Uri(url));
Console.ReadLine();
}
static void DownloadDataCompleted(object sender,
DownloadDataCompletedEventArgs e)
{
byte[] raw = e.Result;
Console.WriteLine(raw.Length + " bytes received");
}
The args contains other bits of information relating to error conditions etc - check those too.
Also note that you'll be coming into DownloadDataCompleted
on a different thread; if you are in a UI (winform, wpf, etc) you'll need to get to the UI thread before updating the UI. From winforms, use this.Invoke
. For WPF, look at the Dispatcher
.
static void Main(string[] args)
{
byte[] data = null;
WebClient client = new WebClient();
client.DownloadDataCompleted +=
delegate(object sender, DownloadDataCompletedEventArgs e)
{
data = e.Result;
};
Console.WriteLine("starting...");
client.DownloadDataAsync(new Uri("http://stackoverflow.com/questions/"));
while (client.IsBusy)
{
Console.WriteLine("\twaiting...");
Thread.Sleep(100);
}
Console.WriteLine("done. {0} bytes received;", data.Length);
}
If anyone using above in web application or websites please set Async = "true" in the page directive declaration in aspx file.
ThreadPool.QueueUserWorkItem(state => WebClientX.DownloadDataAsync(sitesearchURL));
http://workblog.pilin.name/2009/02/system.html
//using ManualResetEvent class
static ManualResetEvent evnts = new ManualResetEvent(false);
static void Main(string[] args)
{
byte[] data = null;
WebClient client = new WebClient();
client.DownloadDataCompleted +=
delegate(object sender, DownloadDataCompletedEventArgs e)
{
data = e.Result;
evnts.Set();
};
Console.WriteLine("starting...");
evnts.Reset();
client.DownloadDataAsync(new Uri("http://stackoverflow.com/questions/"));
evnts.WaitOne(); // wait to download complete
Console.WriteLine("done. {0} bytes received;", data.Length);
}
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