Question

How can I determine if printer is connected?

Typically this application prints to the default printer but in some cases that printer may not be available. If so I don’t want the job sent to it’s queue but rather printed to another available printer.

I understand the PrinterSettings.InstalledPrinters property. Does PrintDocument.PrinterSettings.IsValid return false if a printer is not available?

Does WPF provide this kind of functionality?

My problem is different than Printing problem in C# windows app – Always prints to default printer

Answer 1

First, IsValid checks the value of the PrinterName property to see if it is a valid value, not if the printer is connected.

Second, in WPF it is very easy to do this;

 var defaultPrintQueue = LocalPrintServer.GetDefaultPrintQueue();
 if (!defaultPrintQueue.IsNotAvailable)
 {
   //print stuff
 }

Check the docs for more detail:
In winforms, its a little harder but you can use WMI. Reference System.Management.dll and add the following using statements:

using System;
using System.Drawing.Printing;
using System.Windows.Forms;
using System.Management;

To get all default printers:

NOTE The following code is likely to be OS dependant to some extent. Check the MSDN docs..

 var printerSearcher =
     new ManagementObjectSearcher(
       "SELECT * FROM Win32_Printer where Default = true"
     );
   return printerSearcher.Get();

The WMI documentation for the printer object describes some useful structures we can look at; PrinterStatus and WorkOffline. We can use these to write an utility class to check the availability of the printer, also check its WorkOffline state…

 public static class PrinterUtility
 {
    public static bool IsOnline(this ManagementBaseObject printer)
    {
        var status = printer["PrinterStatus"];
        var workOffline = (bool)printer["WorkOffline"];
        if (workOffline) return false;

        int statusAsInteger = Int32.Parse(status.ToString());
        switch (statusAsInteger)
        {
            case 3: //Idle
            case 4: //Printing
            case 5: //Warming up
            case 6: //Stopped printing
                return true;
            default:
                return false;
        }
    }

    public static ManagementObjectCollection GetDefaultPrinters()
    {
        var printerSearcher =
          new ManagementObjectSearcher(
            "SELECT * FROM Win32_Printer where Default = true"
          );
        return printerSearcher.Get();
    }
}

Now you can combine this with standard WinForms System.Drawing.Printing code:

//in a function, far far away from any button click handler :P
foreach(var printer in PrinterUtility.GetDefaultPrinters())
{
  if (printer.IsOnline())
  {
    var pDoc = new PrintDocument(); //or get from PrintDialog
    pDoc.PrinterSettings.PrinterName = printer["Name"].ToString();
    if (pDoc.PrinterSettings.IsValid) //just check WMI didn't tell fibs about the name
    {
      //do printy things       
    }
  }
}

Hope this helps