Issues with invoke

[rootchord]

I am learning about networking in C# and to do so i am making a simple instant message server/client app. everything is going fine. i am currently testing it by inputting my own ip address as the target to send/receive on same machine.

but, i can only send one message then nothing. when i finally give up and exit the app(running it from vstudio) it gives this error:

System.InvalidOperationException was unhandled
Message=Invoke or BeginInvoke cannot be called on a control until the window handle has been created.
Source=System.Windows.Forms
StackTrace:
at System.Windows.Forms.Control.WaitForWaitHandle(WaitHandle waitHandle)
at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)
at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)
at IMTest.IMForm.AddListBoxItem(Object item) in C:\Users\rootchord\Documents\Visual Studio 2010\Projects\IMTest\IMTest\Form1.cs:line 97
at IMTest.IMForm.ReceiveMessages() in C:\Users\rootchord\Documents\Visual Studio 2010\Projects\IMTest\IMTest\Form1.cs:line 62
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
InnerException: public partial class IMForm : Form
{
TcpListener myList;
public string theirip = "";
IPAddress myip;
private Thread receive;
Socket s;

public IMForm()
{
InitializeComponent();
IPAddress[] localIPs = Dns.GetHostAddresses(Dns.GetHostName());
foreach (IPAddress anip in localIPs)
{
if (!anip.ToString().Contains(":"))
{
myip = anip;
}
}
MessageBox.Show(myip.ToString());
TargetForm settarget = new TargetForm();
settarget.ShowDialog();
theirip = settarget.TargetIPBox.Text;
}

private void Form1_Load(object sender, EventArgs e)
{
receive = new Thread(new ThreadStart(ReceiveMessages));
receive.Start();
this.AcceptButton = SendButton;
}


private void ReceiveMessages()
{
myList = new TcpListener(myip, 8001);
myList.Start();
s = myList.AcceptSocket();
do{
byte[] b = new byte[100];
int k = s.Receive(b);
string message = "";
for (int i = 0; i < k; i++)
{
message += Convert.ToChar(b[i]);
}
AddListBoxItem(message);
}while(true);
}


private void SendMessages(string message)
{
TcpClient tcpclnt = new TcpClient();
try
{
tcpclnt.Connect(theirip, 8001);
}catch(Exception e)
{
MessageBox.Show("Error: " + e);
}

Stream stm = tcpclnt.GetStream();
ASCIIEncoding asen = new ASCIIEncoding();
byte[] ba = asen.GetBytes(message);
stm.Write(ba, 0, ba.Length);

tcpclnt.Close();
}

private delegate void AddListBoxItemDelegate(object item);



private void AddListBoxItem(object item)
{


if (this.ConvBox.InvokeRequired)
{
// This is a worker thread so delegate the task.
this.ConvBox.Invoke(new AddListBoxItemDelegate(this.AddListBoxItem), item);
}
else
{
// This is the UI thread so perform the task.
this.ConvBox.Items.Add(item);
}
}

private void SendButton_Click(object sender, EventArgs e)
{
SendMessages(MessagesBox.Text);
}

private void ConvLabel_Click(object sender, EventArgs e)
{

}

private void label1_Click(object sender, EventArgs e)
{

}

private void ConvBox_SelectedIndexChanged(object sender, EventArgs e)
{

}
}
}

[Mitja Bonca]

Change this method to:

private void AddListBoxItem(object item)
       { 
           if (this.ConvBox.InvokeRequired)
               this.ConvBox.Invoke(new AddListBoxItemDelegate(AddListBoxitem), new object[] {item});
           else
               this.ConvBox.Items.Add(item);
       }

[rootchord]

Thanks soo much for helping me!

but, no change. Same issue.

UPDATE: nevermind, i fixed it! i needed to include the creation of the tcplistener in the dowhile loop. i think i understand why that was the problem, but any expert care to explain precisely what was happening/why that fixed it ?

[samueal]

Hi rootchord

Have you Solved it??

The above Exception states that the window handle should be created for that form..

I have come across the same Exception and i cleared it by creating a window handle!!