Asynchronous Delegates & C++
By Drazen Dotlic, November 01, 2004
Asynchronous delegates let you call synchronous methods in an asynchronous manner. Drazen presents a portableC++ implementation of .NET delegates.
November, 2004: Asynchronous Delegates & C++
Listing 1
namespace Original_Async_Delegate
{
class NetworkBlock
{
public string GetPage(string Url, int Port, bool Secure)
{
// ... fetch the page
return "<html>...</html>";
}
}
class TestAsyncDelegate
{
public delegate string
AsyncGetPage(string Url, int Port, bool Secure);
static void ResultCallback(IAsyncResult ar)
{
AsyncGetPage agp = (AsyncGetPage)ar.AsyncState;
String result = agp.EndInvoke(ar);
}
[STAThread]
static void Main(string[] args)
{
NetworkBlock net = new NetworkBlock();
AsyncGetPage agp = new AsyncGetPage(net.GetPage);
// 1. synchronously wait
IAsyncResult ar1 = agp.BeginInvoke("http...", 80, false, null, null);
string res1 = agp.EndInvoke(ar1);
// 2. wait on async result
IAsyncResult ar2 = agp.BeginInvoke("ftp...", 21, false, null, null);
ar2.AsyncWaitHandle.WaitOne();
string result2 = agp.EndInvoke(ar2);
// 3. loop waiting for completed flag
IAsyncResult ar3 = agp.BeginInvoke("https...", 81, true, null, null);
while(!ar3.IsCompleted)
Thread.Sleep(10);
string result3 = agp.EndInvoke(ar3);
// 4. use async callback for result
IAsyncResult ar4 = agp.BeginInvoke("ftp...", 21, false,
new AsyncCallback(ResultCallback), agp);
}
}
}
