POS for .NET - My program in C# shows text in “Microsoft LineDisplay Simulator” instead of the real display

问题

Hello lovely community!

I am using a HP 2x20 Integrated Display with HP RP 7800 Retail System and decided to play with it and write some small programs for it to learn coding.

The sample tool provided with the SDK works perfectly.

First I wrote a simple program using Microsoft.IO.Ports and simple functions like this:

SerialPort COM3 = new SerialPort("COM3", 9600, Parity.None, 8);
COM3.Open();
COM3.Write(Clear); // string Clear = "\x1B\x40" - hex value of a control character for the display
COM3.Write("Hello community");

It actually worked okay but I didnt manage to apply some of the control characters provided from HP manual and therefore I decided to move on to POS for .NET.

So now straight to the point. I wrote a C# program with basic functionality and buttons.

using Microsoft.PointOfService;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        LineDisplay lineDisplay;
        PosExplorer explorer;
        public Form1()

        {
            InitializeComponent();

            try
            {
                explorer = new PosExplorer(this);
                DeviceCollection devColl = explorer.GetDevices(DeviceType.LineDisplay); // is this line the problem?
                //DeviceCollection devColl = explorer.GetDevice("LineDisplay", "HPLCM220Display"); // this one shows errors so I couldnt use it instead of the line above
                if (devColl == null || devColl.Count <= 0)
                {
                    MessageBox.Show("Device not found");
                    return;
                }
                lineDisplay = (LineDisplay)explorer.CreateInstance(devColl[0]);
                lineDisplay.Open();
                lineDisplay.Claim(10000);
                lineDisplay.DeviceEnabled = true;
                lineDisplay.DisplayText("Hello World.!");
                lineDisplay.DisplayTextAt(1, 0, "Hey MSDN");


            }
            catch (Exception e)
            {
                MessageBox.Show(e.Message);
            }
        }

        private void btn_Clear_Click(object sender, EventArgs e)
        {
            lineDisplay.ClearText();
        }

        private void btn_SendText_Click(object sender, EventArgs e)
        {
            lineDisplay.DisplayText(textBox1.Text);
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            //this.textBox1.TextChanged -= textBox1_TextChanged;
        }
    }
}

And when I launch it it shows me a LineDisplay Simulator which can be cleared and the text can be altered, but the real display doesnt even show anything or gets cleared.

So the question is: how do I make my app show text on my display instead of the simulator. Debugging doesnt really help me. What I noticed is that in AUTOS it shows Microsoft.PointOfService.DeviceSimulators.LineDisplaySimulator in LineDisplay Value so it somehow usess DeviceSimulators but I dont know how and why..

I used POS for .net documentation but sadly didnt succeed https://msdn.microsoft.com/en-us/library/microsoft.pointofservice.linedisplay(v=winembedded.11).aspx

I assume its somehow around - Device Collection line

DeviceCollection devColl = explorer.GetDevices(DeviceType.LineDisplay);
//DeviceCollection devColl = explorer.GetDevice("LineDisplay", "HPLCM220Display");

but if i use the commented line instead of the first une it shows the error:

Error    CS0029    Cannot implicitly convert type 'Microsoft.PointOfService.DeviceInfo' to 'Microsoft.PointOfService.DeviceCollection'    WindowsFormsApplication14    C:\Users\admin\Documents\Visual Studio 2015\Projects\WindowsFormsApplication14\WindowsFormsApplication14\Form1.cs    27    Active

I tried to look for a solution to CS0029 but unfortunately I failed at finding any connection to my problem.

Ive never programmed anything so I am a newbie with shitty code but im striving to learn so please if anybody is so kind to shed some light onto this issue I would be very thankful :)

回答1:

Your machine may have a number of point-of-sale devices (line displays, POS printers, barcode scanners, etc.) attached to it. All these devices are grouped into so-called classes (namely, LineDisplay, PosPrinter, Scanner, etc.) A system may have several devices of one class attached. For example, it is quite common to have two barcode scanners on a regular POS station - a flatbed one to scan normal items and handheld for oversized items.

The PosExplorer class allows you to enumerate all installed POS devices and instantiate selected ones.

The explorer.GetDevices(DeviceType.LineDisplay) returns descriptors of all line displays installed on your system. The descriptors are returned in a collection of type DeviceCollection. Each item in this collection has DeviceInfo type. You may iterate through this collection, check items properties and pick up ones for further manipulation.

The explorer.GetDevice("LineDisplay", "HPLCM220Display") returns descriptor of the exact device by class and name ("HPLCM220Display" line display in your case). The returned descriptor has type DeviceInfo. That's why you had a compilation error - you wouldn't have it if you used the correct class

DeviceInfo devInfo = explorer.GetDevice("LineDisplay", "HPLCM220Display");

Please note, the second parameter to GetDevice() has to be a logical name or an alias of the device. You can list these names by the following command:

"%ProgramFiles%\Microsoft Point Of Service\posdm.exe" ListNames /type:LineDisplay

or (on x64 systems):

"%ProgramFiles(x86)%\Microsoft Point Of Service\posdm.exe" ListNames /type:LineDisplay

After you have found a descriptor (DeviceInfo) of a desired device you may use it to instantiate the device object which provides you with actual interface to control the device:

lineDisplay = (LineDisplay)explorer.CreateInstance(devInfo);

So your code may look like this:

// ...
explorer = new PosExplorer(this);
DeviceInfo devInfo = explorer.GetDevice(DeviceType.LineDisplay, "HPLCM220Display");
if (devInfo == null)
{
    MessageBox.Show("Device not found");
    return;
}
lineDisplay = (LineDisplay)explorer.CreateInstance(devInfo);
lineDisplay.Open();
// ...

Answering the question of devColl[0] and devColl[2] in your comments:

Your system clearly has at least three line displays installed. The first one is a virtual display device installed with POS for .NET SDK. You accessed it via the devColl[0]. Can't say anything about the second. And the third one is your real HP 2x20 Integrated Display which you accessed with the devColl[2] descriptor. You may list all the devices with the posdm command as I've shown above.

来源：https://stackoverflow.com/questions/38975642/pos-for-net-my-program-in-c-sharp-shows-text-in-microsoft-linedisplay-simula

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point-of-sale

opos