Performance Considerations for throwing Exceptions

try
{
    ... // some code
}
catch (Exception ex)
{
    ... // Do something
    throw new CustomException(ex);
}

try
{
    ... // some code
}
catch (Exception ex)
{
    .. // Do something
    throw ex;
}

try
{
    ... // some code
}
catch (Exception ex)
{
    .. // Do something
    throw;
}

try {
        // something that will raise an exception almost half the time
} catch( InsufficientFunds e) {
        // Inform the customer is broke
} catch( UnknownAccount e ) {
        // Ask for a new account number
}

try
{
    // some code
}
catch (Exception ex) { throw ex; }

try
{
    // some code
}
catch (Exception ex) { throw; }

public bool Load(string filepath)
{
  if (File.Exists(filepath)) //Avoid throwing by checking state
  {
    //Wrap anyways in case something changes between check and operation
    try { .... }
    catch (IOException ioFault) { .... }
    catch (OtherException otherFault) { .... }
    return true; //Inform caller of success
  }
  else { return false; } //Inform caller of failure due to state
}