WPF c＃检测哪个键盘通过按键发送（以检测它是否是条形码扫描仪）

Question

I have a USB barcode scanner attached. I'm currently detecting whether key presses were sent to a text box from it via keyups, by having it send a special key combination before it sends the barcode.

However I was wondering if there is another way to do it.

I took at the KeyEventArgs

private void TextBox_KeyUp(object sender, KeyEventArgs e)
{
    this.TextBlock1.Text = e.KeyboardDevice.ToString();
}

I thought e.KeyboardDevice might give me some info on which "keyboard" eg the standard keyboard or the "usb barcode scanner keyboard" but I can't seem to find any of that information.

I just thought there may be a neater way of doing this than sending the special key combination from the barcode scanner and using that.

Answer 1

I've used this answer to solve the same problem in the past. The answer contains a link with full details about the solution. https://stackoverflow.com/a/589326/2696641

Answer 2

I thought Id contribute my solution. Its not that elegant but it only looks for numeric key presses and then looks at the time it takes to respond. If the time is longer than the maximum threshold then it throws out those values from the array. I hope this helps someone.

class BarcodeReader
{
    ArrayList barCode = new ArrayList();
    ArrayList barCodeTimes = new ArrayList();
    ArrayList barCodeDeltaTimes = new ArrayList();
    /// <summary>
    /// Input 1: delayTime (ms) - time for scanner to return values (threshold)[30 seems good],
    /// Input 2: KeyEventArgs - put in key [this.KeyDown += new KeyEventHandler(Form1_KeyDown)],
    /// Output 1: String of barcode read
    /// </summary>
    /// <param name="delayTime"></param>
    /// <param name="e"></param>
    /// <returns></returns>
    public string BarcodeValue(int delayTime, KeyEventArgs e)
    {
        string barCodeString = null;
        var isNumber = e.KeyCode >= Keys.D0 && e.KeyCode <= Keys.D9;
        var rtn = e.KeyCode == Keys.Enter;

        if (isNumber)
        {
            barCode.Add(Encoding.ASCII.GetString(new byte[] { (byte)e.KeyValue }));
            barCodeTimes.Add(DateTime.Now.TimeOfDay.TotalMilliseconds);
        }
        if (rtn)
        {
            barCodeString = ValuesToString(delayTime);
        }
        return barCodeString;
    }
    private string ValuesToString(int delayTime)
    {

        string barCodeString = null;

        foreach (double d in barCodeTimes)
        {
            double diff = 0;
            int index = barCodeTimes.IndexOf(d);
            if (index < barCodeTimes.Count - 1)
            {
                diff = (double)barCodeTimes[index + 1] - (double)barCodeTimes[index];
            }

            barCodeDeltaTimes.Add(diff);
        }
        foreach (double d in barCodeDeltaTimes)
        {
            if (d > delayTime)
            {
                barCode.RemoveAt(0);
            }
        }
        foreach (string s in barCode)
        {
            barCodeString += s;
        }

        barCode.Clear();
        barCodeTimes.Clear();
        barCodeDeltaTimes.Clear();

        return barCodeString;
    }

}