C#

public class UrlBox : TextBox
{
  // ...
  protected override void OnValidating(CancelEventArgs e)
  {
    try
    {
      new Uri(this.Text);
    }
    catch
    {
      e.Cancel = true;
    }
  }
}

using System;
using System.Security;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.Security.Permissions;

namespace ConsoleApplication2
{
	/// <summary>
	/// Summary description for Class1.
	/// </summary>
	class Class1
	{
		[DllImport("advapi32.dll", SetLastError=true)]
		public static extern bool LogonUser(String lpszUsername, String lpszDomain, String lpszPassword, 
			int dwLogonType, int dwLogonProvider, ref IntPtr phToken);

		[DllImport("kernel32.dll", CharSet=System.Runtime.InteropServices.CharSet.Auto)]
		private unsafe static extern int FormatMessage(int dwFlags, ref IntPtr lpSource, 
			int dwMessageId, int dwLanguageId, ref String lpBuffer, int nSize, IntPtr *Arguments);

		[DllImport("kernel32.dll", CharSet=CharSet.Auto)]
		public extern static bool CloseHandle(IntPtr handle);

		[DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
		public extern static bool DuplicateToken(IntPtr ExistingTokenHandle, 
			int SECURITY_IMPERSONATION_LEVEL, ref IntPtr DuplicateTokenHandle);


		// GetErrorMessage formats and returns an error message
		// corresponding to the input errorCode.
		public unsafe static string GetErrorMessage(int errorCode)
		{
			int FORMAT_MESSAGE_ALLOCATE_BUFFER = 0x00000100;
			int FORMAT_MESSAGE_IGNORE_INSERTS = 0x00000200;
			int FORMAT_MESSAGE_FROM_SYSTEM  = 0x00001000;

			int messageSize = 255;
			String lpMsgBuf = "";
			int dwFlags = FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS;

			IntPtr ptrlpSource = IntPtr.Zero;
			IntPtr prtArguments = IntPtr.Zero;
        
			int retVal = FormatMessage(dwFlags, ref ptrlpSource, errorCode, 0, ref lpMsgBuf, messageSize, &prtArguments);
			if (0 == retVal)
			{
				throw new Exception("Failed to format message for error code " + errorCode + ". ");
			}

			return lpMsgBuf;
		}

		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]
		static void Main(string[] args)
		{
			const int LOGON32_PROVIDER_DEFAULT = 0;
			const int LOGON32_LOGON_INTERACTIVE = 2;  //This parameter causes LogonUser to create a primary token.
			const int SecurityImpersonation = 2;

			IntPtr token = new IntPtr(0);
			IntPtr dupToken = new IntPtr(0);

			bool result = LogonUser("frog", "pond", "ribbit", LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, ref token);
			if(result == false)
			{
                                //Could use GetErrorMessage call here...
				Console.WriteLine("Failed to log on.");
				Console.ReadLine();
				return;
			}

			bool dupResult = DuplicateToken(token, SecurityImpersonation, ref dupToken);
			if(dupResult == false)
			{
                                //Could use GetErrorMessage call here...
				Console.WriteLine("Failed to log on.");
				Console.ReadLine();
				return;
			}

			WindowsIdentity newId = new WindowsIdentity(dupToken);
			Console.WriteLine("Impersonation starting.  Windows ID name before  = " + WindowsIdentity.GetCurrent().Name);

			WindowsImpersonationContext impersonatedUser = newId.Impersonate();
			Console.WriteLine("Impersonation complete.  Windows ID name after Impersonate = " + WindowsIdentity.GetCurrent().Name);

			impersonatedUser.Undo();
			Console.WriteLine("Impersonation undone.  Windows ID name after Undo  = " + WindowsIdentity.GetCurrent().Name);

			Console.ReadLine();
		}
	}
}

int todEve = dsAllEvents.Tables["Events"].Select("EventDate Like '*" + date + "*'").Length;
if(todEve>=1)

DataRow[] foundRows = dsAllEvents.Tables["Events"].Select("EventDate Like '*" + date + "*'").Length;
if(foundRows.Length >= 1)

System.Type.GetType("System.String")

typeof(string)

public sealed class AppInfo
{
  private AppInfo() {} // Prevent instantiation
  private static Icon AppIcon; // Private field
  static AppInfo() // Static constructor
  {
    AppIcon = new Icon(typeof(AppInfo), "App.ico");
  }
}

[DllImport("user32.dll")]
private static extern bool SetWindowPos(
  IntPtr hWnd,
  IntPtr hWndInsertAfter,
  [MarshalAs(UnmanagedType.SysInt)] int X,
  [MarshalAs(UnmanagedType.SysInt)] int Y,
  [MarshalAs(UnmanagedType.SysInt)] int cx,
  [MarshalAs(UnmanagedType.SysInt)] int cy,
  [MarshalAs(UnmanagedType.U4)] UINT uFlags);

private const int SWP_NOZORDER = 4;
private const int HWND_TOP = 0;