C # Use WIN32API to get a printer

The enumprinters function in winspool. DRV is mainly used. The Code is as follows:

[Dllimport ("winspool. DRV", setlasterror = true, charset = charset. Auto)]
[Return: financialas (unmanagedtype. bool)]
Private Static extern bool enumprinters ([financialas (unmanagedtype. U4)] printer_enum flags,
[Financialas (unmanagedtype. lpstr)] string sname,
Uint ilevel,
Intptr pprinterdesc,
Uint isize,
[Financialas (unmanagedtype. U4)] ref uint Ineeded,
[Financialas (unmanagedtype. U4)] ref uint ireturned
);

Note: The marshal attribute provides data delivery for hosted and unmanaged code.

The Win32 API of enumprinters is defined as follows:

Bool enumprinters (
DWORD flags, // printer Object Types
Lptstr name, // name of printer object
DWORD level, // information level
Lpbyte pprinterenum, // printer information Buffer
DWORD cbbuf, // size of printer information Buffer
Lpdword encoded needed, // bytes encoded ed or required
Lpdword pcreturned // Number of printers Enumerated
);

The problem is coming again. enumprinters gets printer_info through level, and can getPrinterThe driver is printer_info_2, andC #There is no printer_info_2 structure in, And I am dizzy again .....

After checking the data for half a day, the Internet is basically the definition of printer_info_1, while printer_info_2 is different from printer_info_1. It also includes the devmode structure and the unmanaged structure ~~~~

Finally, we found thatC #It is better to directly use classes to define the structure to correspond to the unmanaged structure. Therefore, two classes are defined.

Printer_info_2 and devmode (Note: Because printer_info_2 only uses the devmode structure to receivePrinterDriver information, so only this class is defined, and no specific implementation is made for other classes ).

In printer_info_2, all data of the DWORD type corresponds to the int32 type, and all data of the lptstr, lpdevmode, and psecurity_descriptor correspond to the intptr pointer type.

In order to obtain the data in the unmanaged database, the following function is used to obtain the data.PrinterInformation

.

Printer_info_2 Pi = new printer_info_2 ();
// Transfers data from the unmanaged memory to the managed memory

For (INT I = 0; I <numprinters; I ++)
{
Marshal. ptrtostructure (prinfo, Pi); // prinfo is obtained by the above enumprintersPrinter

String driver = marshal. ptrtostringauto (PI. pdrivername );

If (printerdriver = "" driver. tolower (). indexof (printerdriver )! =-1)
{

// Handle the problem

}
Prinfo = new intptr (prinfo. toint32 () + marshal. sizeof (typeof (printer_info_2); // get the nextPrinterStart of Information Section
}
.

The problem is now basically solved. HoweverC #It is difficult to call unmanaged functions and encapsulate data between them. If you have time, you need to sort them out.

Source: http://spaces.msn.com/sharkoo/Blog/cns! D8e832ce4545af! 158. Entry

Supplement: In 2.0, the fixed keyword can be used to define a fixed-size array cache, rather than defining a number size as in 1.x. However, this method can only be used for structure (struct), but not for class definition.