How do I search for the default printer and print plain text on a dot matrix printer in .Net?

To pick up the default printer use the PrinterSettings (in English) . Example:

var configImpressora = new PrinterSettings();
Console.WriteLine(configImpressora.PrinterName);

Note that this way you are using the Windows manager to get this information. And what you need to do to send the data is just the opposite.

Unless I do not know anything about it, I doubt that part will help you in anything.

As for the second part of the question:

Essentially you need to write directly to the port, usually PRN or LPT1 or COM1 . sending directly to the port you avoid going through the Windows print manager,

Simplified example (does not have the quality that a production code should have):

var impressora = new System.IO.StreamWriter(@"\.\PRN");
impressora.Write((char)15); //inicia negrito na maioria das impressoras matriciais
impressora.Write("Teste");
impressora.Flush();
impressora.Close();

When I needed to send it to a standard printer, that's basically what I did.

If you need to choose where the printer is on each machine, I'm afraid you should have a local configuration indicating where the printer is. It can be a simple text file, but it can be a local database, the Windows registry or simply allow the user to choose when to print, which can be enough in many cases.

I placed it in Github for future reference .

After a few searches, the way we can do it is not as elegant (we had to call P / Invoke 1 ), but it worked very well.

using System.Drawing.Printing;
(...)
public void ImprimeConteudoDiretamenteNaImpressoraPadrao(string conteudo)
{
    string nomeImpressoraPadrao = (new PrinterSettings()).PrinterName;
    RawPrinterHelper.SendStringToPrinter(nomeImpressoraPadrao, conteudo);
}