C#

delegate void Result(string s);
 
delegate void ExceptionHandler(Exception ex);
  
private void MyCallback(IAsyncResult ar)
{      
    getDNS getIP = (getDNS)ar.AsyncState;      
 
    try
    {
        string result = getIP.EndInvoke(ar);
 
        BeginInvoke(new Result(MyResultMethod), result);
    } 
    catch(Exception ex) // Probably should catch a more specific Exception type.
    {
        BeginInvoke(new ExceptionHandler(MyExceptionHandler), ex);
    }
}
 
private void MyResultMethod(string s)
{
    MessageBox.Show(s);
 
    // Do other updating...
}
 
private void MyExceptionHandlerMethod(Exception ex)
{
    MessageBox.Show(ex.Message);
 
    // Other exception handling code...
}

Leslie Sanford wrote:

private void MyResultMethod(string s)
{    
MessageBox.Show(s);     // Do other updating...
}

for (int x = 0; x < hostList.Count; x++)
{
  getIP.BeginInvoke(hostList[x], new AsyncCallback(MyCallback), getIP);
}

Glen Harvy wrote:

Ok, I've been able to digest most of this but still have my original problem.

How can I "do other updating .." unless I know which hostname that this ip belongs to. I can't figure out how to match this thread with any of the other threads I've created at:-

delegate void Result(string hostName, string result); 
 
delegate void ExceptionHandler(Exception ex);   
 
private void MyCallback(IAsyncResult ar)
{          
    getDNS getIP = (getDNS)ar.AsyncState;           
 
    try    
    {        
        string result = getIP.EndInvoke(ar);         
 
        BeginInvoke(new Result(MyResultMethod), getDNS.HostName, result);    
    }     
    catch(Exception ex) // Probably should catch a more specific Exception type.    
    {        
        BeginInvoke(new ExceptionHandler(MyExceptionHandler), ex);    
    }
} 
 
private void MyResultMethod(string hostName, string result)
{    
    MessageBox.Show(hostName);     // Do other updating...
} 
 
private void MyExceptionHandlerMethod(Exception ex)
{    
    MessageBox.Show(ex.Message);     
 
    // Other exception handling code...
}

Glen Harvy wrote:

I've just noticed that doing what you suggest doesn't actually run more than one call in the calling foreach loop at a time which is not what I wanted. The main thread needs to create at least 20 lookups running in async mode at any one time. Does that make more sense?

IAsyncResult[] results = new IAsyncResult[hostList.Count];
 if (results.Length > 19)
 {
   // need to limit the following to blocks of 20....
 }

 for (int x = 0; x < hostList.Count; x++)
 {
   results[x] = getIP.BeginInvoke(hostList[x], null, null);
 }

 for (int i = 0; i < results.Length; i++)
 {
   // wait 20 seconds for each lookup to complete - otherwise it closes it due to a timeout
   if (results[i].AsyncWaitHandle.WaitOne(20000, true))
   {
     string r = getIP.EndInvoke(results[i]).ToString();
     string[] n = r.Split(new char[1] { '|' });
     DataRow nr = this.myWebLoggerDataSet.Tables["dnscache"].NewRow();
     nr["IP"] = n[1].ToString();
     nr["Name"] = n[0].ToString();
     nr["Date"] = DateTime.Now;
     this.myWebLoggerDataSet.Tables["dnscache"].Rows.Add(nr);
   }
 }
 this.dnscacheTableAdapter.Update(this.myWebLoggerDataSet.dnscache);
 myWebLoggerDataSet.AcceptChanges();