C#

NetworkCredential cred = new NetworkCredential(username, password, domain);
CredentialCache cache = new CredentialCache();
cache.Add(new Uri(url), "Basic", cred);
// ...
admin.Credentials = cache;

using (MyForm form = new MyForm())
{
  form.ShowDialog();
}

MyForm form = null;
try
{
  form = new MyForm();
  form.ShowDialog();
}
finally
{
  if (form != null) ((IDisposable)form).Dispose();
}

object missing = Missing.Value;
axWebBrowser2.ExecWB(
  OLECMDID.OLECMDID_PRINT,
  OLECMDEXECOPT.OLECMDEXECOPT_DONTPROMPTUSER,
  ref missing,
  ref missing);

[DllImport("winspool.dll", CharSet=CharSet.Auto)]
static extern bool SetDefaultPrinter(string printer);

using System;
using System.Management;
using System.Reflection;
 
[assembly: AssemblyVersion("1.0.*")]
[assembly: AssemblyKeyName("dev")]
 
class Printers
{
  static void Main(string[] args)
  {
    EnumeratePrinters(args.Length > 0 ? args[0] : null);
  }
 
  static void EnumeratePrinters(string defaultName)
  {
    ManagementObject defaultPrinter = null;
    ManagementObjectSearcher searcher = new ManagementObjectSearcher(
      "select * from Win32_Printer");
    foreach (ManagementObject printer in searcher.Get())
    {
      string name = printer["Name"].ToString();
      Console.WriteLine("Printer: " + name);
      if (defaultName != null &&
        string.Compare(name, defaultName, true) == 0)
        defaultPrinter = printer;
    }
 
    if (defaultPrinter != null)
    {
      Console.WriteLine("Setting default printer to \"{0}\"",
        defaultPrinter["Name"]);
      defaultPrinter.InvokeMethod("SetDefaultPrinter", null);
    }      
  }
}