barcode Printing asp.net c#

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C#

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

this code use but i have given error in create external function..
--Error: Method has no implementation

static extern SafeFileHandle CreateFile(string lpFileName, FileAccess dwDesiredAccess, uint dwShareMode, IntPtr lpSecurityAttributes, FileMode dwCreationDisposition, uint dwFlagsAndAttributes, IntPtr hTemplateFile);