dotnet/wpf · error · PrintServerException

PrintSystemException.PrintServer.GetDefaultPrinter

Error message

PrintSystemException.PrintServer.GetDefaultPrinter

What it means

Thrown when LocalPrintServer fails to read the default printer while initializing property attributes. The Win32 GetDefaultPrinter call (via the spooler) failed, and the InternalPrintSystemException is rethrown as a PrintSystemException with the GetDefaultPrinter key.

Solutions

  1. Check whether a default printer exists (GetDefaultPrinter Win32 / Settings > Printers) before accessing DefaultPrintQueue.
  2. Start the Print Spooler service if it is stopped.
  3. Run the code in an interactive user session that has printer configuration, not a bare service context.
  4. Set a default printer programmatically or manually, or handle the null/no-default case explicitly.

Example fix

// before
PrintQueue queue = new LocalPrintServer().DefaultPrintQueue; // throws when none set
// after
var server = new LocalPrintServer();
var queue = server.GetPrintQueues().FirstOrDefault();
if (queue != null) server.DefaultPrintQueue = queue;
var target = server.DefaultPrintQueue ?? queue;
Defensive patterns

Strategy: fallback

Validate before calling

static bool HasDefaultPrinter()
{
    var ps = new LocalPrintServer();
    return ps.GetPrintQueues().Any();
}

Type guard

static bool TryGetDefaultQueue(LocalPrintServer server, out PrintQueue? queue)
{
    queue = server.GetPrintQueues().FirstOrDefault();
    return queue != null;
}

Try / catch

PrintQueue? target;
try { target = server.DefaultPrintQueue; }
catch (PrintSystemException)
{
    target = server.GetPrintQueues().FirstOrDefault(); // fall back to first available
}

Prevention

When it happens

Trigger: Accessing LocalPrintServer.DefaultPrintQueue (or refresh of the DefaultPrintQueue attribute) on a machine where no default printer is set, or where GetDefaultPrinter fails due to spooler issues or permissions.

Common situations: Fresh Windows installs / server cores with no printers configured; service accounts and IIS app pools with no user printer profile; Spooler service stopped; RDS sessions without printer redirection.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/f89755303c5ed183. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/System.Printing/CPP/src/LocalPrintServer.cpp:940

                    else
                    {
                        //
                        // This means that this is not a Connection.
                        // Could be something else other than a local
                        // printer, but we don't care at this stage
                        //
                        targetPrintServer = this;
                    }
                    attributeValue->Value = gcnew PrintQueue(targetPrintServer,
                                                             defaultPrinterName);
                }

                attributeValue->IsInternallyInitialized = false;

            }
            catch (InternalPrintSystemException^ internalException)
            {
                throw CreatePrintServerException(internalException->HResult, "PrintSystemException.PrintServer.GetDefaultPrinter");
            }
        }
    }
}

/*++

Routine Name:

    GetUnInitializedData

Routine Description:

    Initialize an array of properties with data from the Spooler service.

Arguments:

    properties - array of string representing the properties to be initialized

View on GitHub (pinned to 81131a70a4)