How to get the list of all printers in computer

Try this:

foreach (string printer in System.Drawing.Printing.PrinterSettings.InstalledPrinters)
{
    MessageBox.Show(printer);
}

If you need more information than just the name of the printer you can use the System.Management API to query them:

var printerQuery = new ManagementObjectSearcher("SELECT * from Win32_Printer");
foreach (var printer in printerQuery.Get())
{
    var name = printer.GetPropertyValue("Name");
    var status = printer.GetPropertyValue("Status");
    var isDefault = printer.GetPropertyValue("Default");
    var isNetworkPrinter = printer.GetPropertyValue("Network");

    Console.WriteLine("{0} (Status: {1}, Default: {2}, Network: {3}", 
                name, status, isDefault, isNetworkPrinter);
}