RawInput from different Keyboard C# .Net

Question

I am working on a Windows Forms Application that should get data from a USB Scale. The USB scale is handled like a Keyboard. If someone puts something on the scale, the scale starts to type the weight String like a USB Keyboard. Before, I'd let the scale type the Weight String into a Textbox by clicking into textBox in the Forms App. But now I need to obtain the weight string intern without letting the Scale write directly into a textBox. So that the Program can process the data from the scale while it is in Background.

So at first I think I have to choose a Device for the Input. (something like Keyborad on Com Port XY) So I need to create a List including all Input Devices. How do I do this in C# .Net?

I already tried:

string[] devices = GetRawInputDeviceList;
textBox1.Text = devices[0];
textBox2.Text = devices[1];

But this is not working. Could maybe someone tell me how to do that? Or what do you guys think is the best way to solve my Problem? Please Help!

This post has interesting links on this subject: codeproject.com/Questions/242099/… — Olivier Jacot-Descombes
– Olivier Jacot-Descombes, Commented Mar 10, 2017 at 18:32
When trying to write in to the Textboxes it says: "An unhandled exception of type 'System.NullReferenceException' occurred in ScaleCalc75.exe". — Sardar Agabejli
– Sardar Agabejli, Commented Mar 10, 2017 at 18:36
In debug mode, Visual Studio tells you the file name, the line number and the column number of where the exception occurs. Set a break point there and debug! — Olivier Jacot-Descombes
– Olivier Jacot-Descombes, Commented Mar 11, 2017 at 21:50

Sardar Agabejli · Accepted Answer · 2017-03-15 00:36:54Z

I want to inform you that the following code helped me solving my Problem. You will need Mike O’Brien’s USB HID library. You can download it in VisualStudio (NuGet Packages) or here: https://github.com/mikeobrien/HidLibrary

using System;
using System.Linq;
using System.Text;
using HidLibrary;

namespace HIDProject
{
    class Program
    {
        private const int VendorId = 0x0801;
        private const int ProductId = 0x0002;

        private static HidDevice _device;

        static void Main()
        {
            _device = HidDevices.Enumerate(VendorId, ProductId).FirstOrDefault();

            if (_device != null)
            {
                _device.OpenDevice();

                _device.Inserted += DeviceAttachedHandler;
                _device.Removed += DeviceRemovedHandler;

                _device.MonitorDeviceEvents = true;

                _device.ReadReport(OnReport);

                Console.WriteLine("Reader found, press any key to exit.");
                Console.ReadKey();

                _device.CloseDevice();
            }
            else
            {
                Console.WriteLine("Could not find reader.");
                Console.ReadKey();
            }
        }

        private static void OnReport(HidReport report)
        {
            if (!_device.IsConnected) { return; }

            var cardData = new Data(report.Data);

            Console.WriteLine(!cardData.Error ? Encoding.ASCII.GetString(cardData.CardData) : cardData.ErrorMessage);

            _device.ReadReport(OnReport);
        }

        private static void DeviceAttachedHandler()
        {
            Console.WriteLine("Device attached.");
            _device.ReadReport(OnReport);
        }

        private static void DeviceRemovedHandler()
        {
            Console.WriteLine("Device removed.");
        }
    }
}

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