Visual Basic

Public Function IsInternetAvailable() as Boolean<br />
   Dim oUrl As New System.Uri("http://www.yoursite.com/") 'Change to web address you wish to check<br />
   Dim oWebRequest As System.Net.WebRequest<br />
   Dim oResponse as System.Net.Response<br />
<br />
   Try<br />
      oResponse = oWebRequest.GetResponse<br />
      oResponse.Close()<br />
      oWebRequest = Nothing<br />
      Return True<br />
   Catch ex as Exception<br />
      oResponse.Close()<br />
   Finally<br />
      oResponse.Close()<br />
      oWebResponse = Nothing<br />
   End Try<br />
End Function

If IsInternetAvailable() Then<br />
   Messagebox.Show("you are online !!!")<br />
End If

If Not IsNumeric(e.KeyChar)  Then<br />
            MessageBox.Show("Write Only Numbers")<br />
            e.Handled = True <br />
EndIf

dim source as string = "This is a search"<br />
dim source2 as string  = "This a atring"<br />
dim search  as string = "This is"<br />
<br />
Console.WriteLine(source.IndexOf(search)) ' Prints "0" as the search exists at position 0<br />
Console.WriteLine(source2.IndexOf(search)) ' Prints "-1" as the search does not exist at all

foreach(Control control in myForm.Controls)
{
  if(control is TextBox)
  {
    // do something with a textbox
  }
  else if(control is ComboBox)
  {
    // do something with combo box
  }
  // etc.
}