VisaNS MessageBasedSession BeginWrite is not calling callback async method

[BabaGoud]

Hello team,

I was trying the below code in  a C# Winform application , in the writeSession() method once the BeginWrite is done, it needs to call the AsyncCallBack method OnWriteComplete(), which is not happening, I do not see any exception or error. Could you please check if I am doing anything wrong?

private MessageBasedSession mbSession;
private IAsyncResult asyncHandle = null;

private void writeSession(string command)
{
try
{
SetupWaitingControlState(true);
string textToWrite = ReplaceCommonEscapeSequences("?C");
asyncHandle = mbSession.BeginWrite(
textToWrite,
new AsyncCallback(OnWriteComplete),
(object)textToWrite.Length);
OnWriteComplete(asyncHandle);
}
catch (Exception exp)
{
MessageBox.Show(exp.Message);
}
}

private string ReplaceCommonEscapeSequences(string s)
{
try
{
return (s != null) ? s.Replace("\\n", "\n").Replace("\\r", "\r") : s;
}
catch (Exception ex)
{
log.Error("Exception in" + MethodBase.GetCurrentMethod(), ex);
return null;
}
}

private void OnWriteComplete(IAsyncResult result)
{
try
{
SetupWaitingControlState(false);
mbSession.EndWrite(result);
ioStatusLabel.Text = "I/O Status:" + mbSession.LastStatus.ToString();
writeLabel.Text = "Write: " + ((int)result.AsyncState).ToString();

// Always perform a read after a Write
readSessionsButton_Click(null, null);
}
catch (Exception exp)
{
MessageBox.Show(exp.Message);
}
}

[SaileshK]

Hi,

Please ensure you are creating the new AsyncCallback as defined in the documentation for the BeginRead Method

[BabaGoud]

Thank you for the reply. If you see my code above, I am using new AsyncCallback as the parameter to BeginWrite().

Moreover I have another problem where the below overloaded version of BeginWrite() always returns the AsyncState as null. Below is the code please let me know if anything is wrong. I have the session created as well.

string textToWrite = ReplaceCommonEscapeSequences("?C");
byte[] bytes = Encoding.ASCII.GetBytes(textToWrite);
IAsyncResult asyncHandle = mbSession.BeginWrite(bytes,0,bytes.Length);

But the below overloaded version of BeginWrite with AsyncCallback code returns a value for AsyncState.

asyncHandle = mbSession.BeginWrite(textToWrite, new AsyncCallback(OnWriteComplete),(object)textToWrite.Length);