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// This code will not compile!

static void Main(string[] args)

{

Console.WriteLine("***** Handling Multiple Exceptions *****\n");

Car myCar = new Car("Rusty", 90);

try

{

// Trip Arg out of range exception.

myCar.Accelerate(-10);

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8849CH07.qxd  10/1/07  10:38 AM  Page 236

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}

catch(Exception e)

{

// Process all other exceptions?

Console.WriteLine(e.Message);

}

catch (CarIsDeadException e)

{

Console.WriteLine(e.Message);

}

catch (ArgumentOutOfRangeException e)

{

Console.WriteLine(e.Message);

}

Console.ReadLine();

}

This exception-handling logic generates compile-time errors. The problem is due to the fact

that the first catch block can handle anything derived from System.Exception (given the “is-a” rela-

tionship), including the CarIsDeadException and ArgumentOutOfRangeException types. Therefore, the

final two catch blocks are unreachable!

The rule of thumb to keep in mind is to make sure your catch blocks are structured such that

the very first catch is the most specific exception (i.e., the most derived type in an exception type

inheritance chain), leaving the final catch for the most general (i.e., the base class of a given excep-

tion inheritance chain, in this case System.Exception).

Thus, if you wish to define a catch block that will handle any errors beyond CarIsDeadException

and ArgumentOutOfRangeException, you would write the following: