C# 多个线程一直跑着While(true)

Thread dataThread = new Thread(delegate()
{
while (threadFlag)
{
if (Port != null && Port.IsOpen)
{
length = Port.BytesToRead;
if (length > 0)
{

bytes = new byte[length];
Port.Read(bytes, 0, length);

tcp.SendData(bytes);

if (textBox.InvokeRequired)
{

textBox.Invoke(new Action<string>(s =>
{
textBox.AppendText(s + Environment.NewLine);
textBox.SelectionStart = textBox.TextLength;
textBox.ScrollToCaret();

}), System.Text.Encoding.ASCII.GetString(bytes));

}
else
{
textBox.AppendText(System.Text.Encoding.ASCII.GetString(bytes) + Environment.NewLine);
textBox.SelectionStart = textBox.TextLength;
textBox.ScrollToCaret();

}
}

}
Thread.Sleep(1);
}

});
dataThread.IsBackground = true;
dataThread.Name = PortName;
dataThread.Start();
}

}