.NET code to send ZPL to Zebra printers

Take a look at this thread: Print ZPL codes to ZEBRA printer using PrintDocument class.

Specifically the OP pick this function from the answers to the thread:

[DllImport("kernel32.dll", SetLastError = true)]
static extern SafeFileHandle CreateFile(string lpFileName, FileAccess dwDesiredAccess,
uint dwShareMode, IntPtr lpSecurityAttributes, FileMode dwCreationDisposition,
uint dwFlagsAndAttributes, IntPtr hTemplateFile);

private void Print()
{
    // Command to be sent to the printer
    string command = "^XA^FO10,10,^AO,30,20^FDFDTesting^FS^FO10,30^BY3^BCN,100,Y,N,N^FDTesting^FS^XZ";

    // Create a buffer with the command
    Byte[] buffer = new byte[command.Length];
    buffer = System.Text.Encoding.ASCII.GetBytes(command);
    // Use the CreateFile external func to connect to the LPT1 port
    SafeFileHandle printer = CreateFile("LPT1:", FileAccess.ReadWrite, 0, IntPtr.Zero, FileMode.Open, 0, IntPtr.Zero);
    // Aqui verifico se a impressora é válida
    if (printer.IsInvalid == true)
    {
        return;
    }

    // Open the filestream to the lpt1 port and send the command
    FileStream lpt1 = new FileStream(printer, FileAccess.ReadWrite);
    lpt1.Write(buffer, 0, buffer.Length);
    // Close the FileStream connection
    lpt1.Close();

}

I've managed a project that does this with sockets for years. Zebra's typically use port 6101. I'll look through the code and post what I can.

public void SendData(string zpl)
{
    NetworkStream ns = null;
    Socket socket = null;

    try
    {
        if (printerIP == null)
        {
            /* IP is a string property for the printer's IP address. */
            /* 6101 is the common port of all our Zebra printers. */
            printerIP = new IPEndPoint(IPAddress.Parse(IP), 6101);  
        }

        socket = new Socket(AddressFamily.InterNetwork,
            SocketType.Stream,
            ProtocolType.Tcp);
        socket.Connect(printerIP);

        ns = new NetworkStream(socket);

        byte[] toSend = Encoding.ASCII.GetBytes(zpl);
        ns.Write(toSend, 0, toSend.Length);
    }
    finally
    {
        if (ns != null)
            ns.Close();

        if (socket != null && socket.Connected)
            socket.Close();
    }
}

Figured since this is still showing up high in search results for C# and ZPL I should mention SharpZebra. It's only EPL2, but I've submitted an update that adds ZPL support along with printing via sockets, the Windows Spool Service and direct USB.

@liquide's answer works great.

System.IO.File.Copy(inputFilePath, printerPath);

Which I found from the Zebra's ZPL Programmer's Guide Volume 1 (2005)