Execute long time command in SSH.NET and display t

Is there any way to execute Linux command and display the result in text box in Windows application like PuTTY.

For example I'm trying to execute the following commands

wget http://centos-webpanel.com/cwp-latest
sh cwp-latest

using the following code

SshClient sshclient = new SshClient(IPtxtBox.Text, UserNameTxt.Text, PasswordTxt.Text);
sshclient.Connect();
ShellStream stream = sshclient.CreateShellStream("customCommand", 80, 24, 800, 600, 1024);

resultTxt.Text = SSHCommand.SendCommand(stream, "wget http://centos-webpanel.com/cwp-latest && sh cwp-latest");

private static void WriteStream(string cmd, StreamWriter writer, ShellStream stream)
{
    writer.WriteLine(cmd);
    while (stream.Length == 0)
        Thread.Sleep(500);
}
private static string ReadStream(StreamReader reader)
{
    StringBuilder result = new StringBuilder();

    string line;
    while ((line = reader.ReadLine()) != null)
        result.AppendLine(line);

    return result.ToString();
}
private static string SendCommand(ShellStream stream, string customCMD)
{
    StringBuilder strAnswer = new StringBuilder();

    var reader = new StreamReader(stream);
    var writer = new StreamWriter(stream);
    writer.AutoFlush = true;
    WriteStream(customCMD, writer, stream);

    strAnswer.AppendLine(ReadStream(reader));

    string answer = strAnswer.ToString();
    return answer.Trim();
}

This command takes along time to be executed and no result appeared on the result text box.

First, do not use "shell" channel to automate a command execution, unless you have a good reason. Use "exec" channel (CreateCommand or RunCommand in SSH.NET).

To feed the output to a TextBox, just keep reading the stream on a background thread:

private void button1_Click(object sender, EventArgs e)
{
    new Task(() => RunCommand()).Start();
}

private void RunCommand()
{
    var host = "hostname";
    var username = "username";
    var password = "password";

    using (var client = new SshClient(host, username, password))
    {
        client.Connect();
        // If the command2 depend on an environment modified by command1,
        // execute them like this.
        // If not, use separate CreateCommand calls.
        var cmd = client.CreateCommand("command1; command2");

        var result = cmd.BeginExecute();

        using (var reader =
                   new StreamReader(cmd.OutputStream, Encoding.UTF8, true, 1024, true))
        {
            while (!result.IsCompleted || !reader.EndOfStream)
            {
                string line = reader.ReadLine();
                if (line != null)
                {
                    textBox1.Invoke(
                        (MethodInvoker)(() =>
                            textBox1.AppendText(line + Environment.NewLine)));
                }
            }
        }

        cmd.EndExecute(result);
    }
}

For a slightly different approach, see a similar WPF question: SSH.NET real-time command output monitoring.