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// This time, tell the compiler to add CIL code

// to throw an exception if overflow/underflow

// takes place.

try

{

byte sum = checked((byte)Add(b1, b2));

Console.WriteLine("sum = {0}", sum);

}

catch (OverflowException ex)

{

Console.WriteLine(ex.Message);

}

}

Notice that the return value of Add() has been wrapped within the scope of the checked key-

word. Since the sum is greater than a byte, we trigger a runtime exception. Notice the error message

printed out via the Message property in Figure 3-16.

Figure 3-16.

The checked keyword forces runtime exceptions to be thrown when data loss occurs.

If you wish to force overflow checking to occur over a block of code statements, you can do so

by defining a 

checked scope as follows:

try

{

checked

{

byte sum = (byte)Add(b1, b2);

Console.WriteLine("sum = {0}", sum);

}

}

catch (OverflowException ex)

{

Console.WriteLine(ex.Message);

}

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In either case, the code in question will be evaluated for possible overflow conditions automat-

ically, which will trigger an overflow exception if encountered.