Windows forms timer not waiting for method to return

Question

I'm having a problem with my windows forms timer, which is supposed call a method that reads data from serial using Serial.ReadExisting(). I often get multiple calls from the timer when my com port is attempting to send data over, which breaks a single string into multiple strings. This bothers me, as I put a timestamp in front of the returning string and append it to a multiline textbox. Is there any way for the timer to wait until the method has finished reading the incoming data without having to delay/slow down my timer?

What I have so far:

private void loop_Tick(object sender, EventArgs e)
{
    AddToTextBox(Program.SerialReadLine());
}

And

public static string SerialReadLine()
{
    string read = _serialPort.ReadExisting();
    return read;
}

Answer 1

You can disable the timer, do the call and enable it again.

private void loop_Tick(object sender, EventArgs e)
{
    loop.Enabled = false;
    try
    {
        AddToTextBox(Program.SerialReadLine());
    }
    finally
    {
        loop.Enabled = true;
    }
}