Hello everybody,

I'm using a dotmatrix printer (EPSON LX-300+) in order to print line
by line.
Starting from the MSDN Article #322091 "HOW TO: Send Raw Data to a
Printer by Using Visual C# .NET"
(http://support.microsoft.com/default.aspx?scid=kb;EN-US;322091),
all is fine till there ;

I'm trying to configure the printer to choose the character set (I'm
French).
By means of the printer user guide, I identified the sequence : ESC R
1

I'm facing with the following problem :

To send an escape sequence, 2 functions (APIs) are necessary :
- CreateDC(), to obtain a device context of the printer ;
- Escape(), to send the sequence using the DC.

I always have the same error with Escape() : "Descripteur non valide"
/ "Invalid Descriptor" and a return value of zero.
I have tried with other sequence (bold, italic...) with no success.

Any ideas ?

Any help will be appreciated.
Thanks in advance.

Jean-Louis.

Here is the code (some is omitted for clearness) :
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.
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[DllImport("gdi32.dll", EntryPoint="Escape", SetLastError=true,
ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
public static extern long Escape(long hdc, long nEscape, long nCount,
string lpInData, object lpOutData);

[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]
internal struct structDevMode
{
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public String
        dmDeviceName;
    [MarshalAs(UnmanagedType.U2)] public short dmSpecVersion;
    [MarshalAs(UnmanagedType.U2)] public short dmDriverVersion;
    [MarshalAs(UnmanagedType.U2)] public short dmSize;
    [MarshalAs(UnmanagedType.U2)] public short dmDriverExtra;
    [MarshalAs(UnmanagedType.U4)] public int dmFields;
    [MarshalAs(UnmanagedType.I2)] public short dmOrientation;
    [MarshalAs(UnmanagedType.I2)] public short dmPaperSize;
    [MarshalAs(UnmanagedType.I2)] public short dmPaperLength;
    [MarshalAs(UnmanagedType.I2)] public short dmPaperWidth;
    [MarshalAs(UnmanagedType.I2)] public short dmScale;
    [MarshalAs(UnmanagedType.I2)] public short dmCopies;
    [MarshalAs(UnmanagedType.I2)] public short dmDefaultSource;
    [MarshalAs(UnmanagedType.I2)] public short dmPrintQuality;
    [MarshalAs(UnmanagedType.I2)] public short dmColor;
    [MarshalAs(UnmanagedType.I2)] public short dmDuplex;
    [MarshalAs(UnmanagedType.I2)] public short dmYResolution;
    [MarshalAs(UnmanagedType.I2)] public short dmTTOption;
    [MarshalAs(UnmanagedType.I2)] public short dmCollate;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public String
dmFormName;
    [MarshalAs(UnmanagedType.U2)] public short dmLogPixels;
    [MarshalAs(UnmanagedType.U4)] public int dmBitsPerPel;
    [MarshalAs(UnmanagedType.U4)] public int dmPelsWidth;
    [MarshalAs(UnmanagedType.U4)] public int dmPelsHeight;
    [MarshalAs(UnmanagedType.U4)] public int dmNup;
    [MarshalAs(UnmanagedType.U4)] public int dmDisplayFrequency;
    [MarshalAs(UnmanagedType.U4)] public int dmICMMethod;
    [MarshalAs(UnmanagedType.U4)] public int dmICMIntent;
    [MarshalAs(UnmanagedType.U4)] public int dmMediaType;
    [MarshalAs(UnmanagedType.U4)] public int dmDitherType;
    [MarshalAs(UnmanagedType.U4)] public int dmReserved1;
    [MarshalAs(UnmanagedType.U4)] public int dmReserved2;
}

[DllImport("GDI32.dll", EntryPoint="CreateDC", SetLastError=true,
    CharSet=CharSet.Unicode, ExactSpelling=false,
    CallingConvention=CallingConvention.StdCall)]
internal static extern long CreateDC([MarshalAs(UnmanagedType.LPTStr)]
    string pDrive,
    [MarshalAs(UnmanagedType.LPTStr)] string pName,
    [MarshalAs(UnmanagedType.LPTStr)] string pOutput,
    ref structDevMode pDevMode);
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.
.

public static void Init ()
{
    const long PASSTHROUGH = 19;
    const long NULL = 0;
    long ret;

    string escCar = ((char)27).ToString();
    string escString = escCar + "R1";

    try
    {
        structDevMode pDevMode = new structDevMode();
        long hdcPrint = CreateDC( "winspool", "EPSON LX", "", ref pDevMode);
        ret = Escape(hdcPrint, PASSTHROUGH, escString.Length, escString,
NULL);

        // ALWAYS true here \/
        if (ret == 0)
        {
            Win32Exception ex = new Win32Exception();
            Console.WriteLine ex.Message;
        }
    }
    catch(Exception _ex)
    {
        Console.WriteLine (_ex);
    }
}