Using this KB Article as an example: http://support.microsoft.com/kb/322091/en-us ,
I'm trying to send raw data (byte array) to a thermal printer. For this I use the following method from the above article:
public static bool SendBytesToPrinter(string szPrinterName, IntPtr pBytes, Int32 dwCount)
{
Int32 dwError = 0, dwWritten = 0;
IntPtr hPrinter = new IntPtr(0);
DOCINFOA di = new DOCINFOA();
bool bSuccess = false; // Assume failure unless you specifically succeed.
di.pDocName = "My C#.NET RAW Document";
di.pDataType = "RAW";
// Open the printer.
if (OpenPrinter(szPrinterName.Normalize(), out hPrinter, IntPtr.Zero))
{
// Start a document.
if (StartDocPrinter(hPrinter, 1, di))
{
// Start a page.
if (StartPagePrinter(hPrinter))
{
// Write your bytes.
bSuccess = WritePrinter(hPrinter, pBytes, dwCount, out dwWritten);
EndPagePrinter(hPrinter);
}
EndDocPrinter(hPrinter);
}
ClosePrinter(hPrinter);
}
// If you did not succeed, GetLastError may give more information
// about why not.
if (bSuccess == false)
{
dwError = Marshal.GetLastWin32Error();
}
return bSuccess;
}
So I send an array:
bool bSuccess = false;
...
try
{
bSuccess = RawPrinterHelper.SendBytesToPrinter(printerName, pUnmanagedBytes, nLength);
}
catch (Exception ex)
{
failprint = ex.Message;
}
if (bSuccess == true)
{
MessageBox.Show("Text printed");
}
else
{
MessageBox.Show("Printing failed: " + failprint);
}
If the printer is available, all goes ok and I get MessageBox.Show("Text printed");
together with actual printing. But if I turn off the printer (before the attempt to print), I dont get Printing failed MessageBox. Instead the application gets frozen and waits until the printer is turned on, then the queued print job successfully gets printed, application gets unfrozen and I get MessageBox.Show("Text printed")
.
Where am I wrong in my attempt to catch the failed print job, without the application getting in frozen, waiting state?
You should run WritePrinter Method asynchronously And then check Marshal.GetLastWin32Error();
This is old school. You might want to use this
// Create the printer server and print queue objects
LocalPrintServer localPrintServer = new LocalPrintServer();
PrintQueue defaultPrintQueue = LocalPrintServer.GetDefaultPrintQueue();
// Call AddJob
PrintSystemJobInfo myPrintJob = defaultPrintQueue.AddJob();
// Write a Byte buffer to the JobStream and close the stream
Stream myStream = myPrintJob.JobStream;
Byte[] myByteBuffer = UnicodeEncoding.Unicode.GetBytes("This is a test string for the print job stream.");
myStream.Write(myByteBuffer, 0, myByteBuffer.Length);
myStream.Close();
source msdn
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