Monitoring a folder for new files in .net can easily be watched using the FileSystemWatcher in System.IO. You give it a path (ie: C:\toprint) and it will raise an event when a file is created (you can also watch for deleted, renamed and updated files).

Edit: I have new / full code here on GitHub.

I’ve had the need on several occasions to print new files as they are created, so the combination of the FileSystemWatcher and using a process to call the file and print work well together. Below the code to print to the default printer (works great for .pdf files):

c#:

 Process PrintProcess = new Process();
 PrintProcess.StartInfo.CreateNoWindow = false;
 PrintProcess.StartInfo.Verb = "print";
 PrintProcess.StartInfo.FileName = e.FullPath;
 PrintProcess.Start();

vb:

 Dim PrintProcess As New Process
 PrintProcess.StartInfo.CreateNoWindow = False
 PrintProcess.StartInfo.Verb = "print"
 PrintProcess.StartInfo.FileName = e.FullPath
 PrintProcess.Start()

The file watcher uses this syntax:

c#:

FileSystemWatcher fsWatcher = new FileSystemWatcher(txtDirToWatch.Text);

fsWatcher.Created += OnChanged;

 var withFSW = fsWatcher;
 withFSW.EnableRaisingEvents = true;
 withFSW.IncludeSubdirectories = false;
 withFSW.WaitForChanged(WatcherChangeTypes.Created);
 withFSW.Filter = "*.pdf";

vb:

Dim fsWatcher As New FileSystemWatcher(txtDirToWatch.Text)
 
AddHandler fsWatcher.Created, AddressOf OnChanged

With fsWatcher
 .EnableRaisingEvents = True
 .IncludeSubdirectories = False
 .WaitForChanged(WatcherChangeTypes.Created)
 .Filter = "*.pdf"

End With

And the OnChanged Event: c#:

 public void OnChanged(object source, FileSystemEventArgs e)
 {
   //Do something with e.FullPath, etc.
 }

 

vb:

 Public Sub OnChanged(ByVal source As Object, ByVal e As FileSystemEventArgs)
  'Do something with e.FullPath, etc.
 End Sub

 

*I haven’t used this method to print many different formats or tons of files at once, but give it a try!

If you’d like a fully working solution (vb or c#) drop me a line at chris.bitting(at)gmail(dot)com and I’d be glad to send my project and code.