// The finally Block
// ---------------------------------------------------------------------------------------------------------------
// A try/catch scope may also define an optional finally block.The purpose of a finally block is to ensure
// that a set of code statements will always execute, exception(of any type) or not.To illustrate, assume you
// want to always power down the car’s radio before exiting Main(), regardless of any handled exception.
// In a more real-world scenario, when you need to dispose of objects, close a file, or detach from
// a database(or whatever), a finally block ensures a location for proper cleanup.
public static void ExampleCar54()
{
Console.WriteLine("***** Handling Multiple Exceptions *****\n");
Car5 myCar = new Car5("Rusty", 90);
myCar.CrankTunes(true);
try
{
// Speed up car logic.
}
catch (CarIsDeadException e)
{
// Process CarIsDeadException.
}
catch (ArgumentOutOfRangeException e)
{
// Process ArgumentOutOfRangeException.
}
catch (Exception e)
{
// Process any other Exception.
}
finally
{
// This will always occur. Exception or not.
myCar.CrankTunes(false);
}
}
// Rethrowing Exceptions
// ---------------------------------------------------------------------------------------------------------------
// Be aware that if the Method is the Main() method, the ultimate receiver of Exception is the CLR because it
// is the Main() method rethrowing the exception.Because of this, your end user is presented with a system
// supplied error dialog box.Typically, you would only rethrow a partial handled exception to a caller
// that has the ability to handle the incoming exception more gracefully.
// Notice as well that you are not explicitly rethrowing the Exception object but rather making
// use of the throw keyword with no argument. You’re not creating a new exception object; you’re just
// rethrowing the original exception object (with all its original information). Doing so preserves
// the context of the original target.
public static void ExampleCar53()
{
Console.WriteLine("***** Custom Exception Example53 *****");
Console.WriteLine("=> Creating a car and stepping on it!");
Car5 myCar = new Car5("Zippy", 90);
myCar.CrankTunes(true);
try
{
// trip exception
myCar.Accelerate(-10);
}
catch (Exception ex)
{
throw;
}
// The error has been handled, processing continues with the next statement.
Console.WriteLine("\n----------- Out of exception logic ----------- ");
// separator
Console.WriteLine("".PadLeft(40, '='));
}
// Exception Filters
// ---------------------------------------------------------------------------------------------------------------
// C# 6 introduced a new clause that can be placed on a catch scope, via the when keyword. When you add
// this clause, you have the ability to ensure that the statements within a catch block are executed only if some
// condition in your code holds true. This expression must evaluate to a Boolean (true or false) and can be
// obtained by using a simple code statement in the when definition itself or by calling an additional method in
// your code.In a nutshell, this approach allows you to add “filters” to your exception logic.
// First, assume you have added a few custom properties to your CarIsDeadException.
public static void ExampleCar55()
{
Console.WriteLine("***** Exception Filtering with When Clause Test55 *****");
Console.WriteLine("=> Creating a car and stepping on it!");
Car5 myCar = new Car5("Zippy", 90);
myCar.CrankTunes(true);
try
{
// trip exception
myCar.Accelerate(-10);
}
catch (CarIsDeadException ex) when(ex.ErrorTimeStamp.DayOfWeek != DayOfWeek.Friday)
{
Console.WriteLine($"-------------- CarIsDeadException, when day is not Friday --------------");
Console.WriteLine($"ex.Message : {ex.Message}");
Console.WriteLine($"ex.ErrorTimeStamp : {ex.ErrorTimeStamp}");
Console.WriteLine($"ex.CauseOfError : {ex.CauseOfError}");
}
catch (ArgumentOutOfRangeException ex)
{
Console.WriteLine($"-------------- ArgumentOutOfRangeException --------------");
Console.WriteLine($"ex.Message : {ex.Message}");
}
// This will catch any other exception
// beyond CarIsDeadException or
// ArgumentOutOfRangeException.
catch (Exception e)
{
Console.WriteLine($"-------------- Exception --------------");
Console.WriteLine(e.Message);
}
// The error has been handled, processing continues with the next statement.
Console.WriteLine("\n----------- Out of exception logic ----------- ");
// separator
Console.WriteLine("".PadLeft(40, '='));
}