Programmers are well aware that many arthmetic operation on primitives could result in an overflow:
Byte b =100;
b = (Byte)(b+200);
In most programming scenarios, this silent overflow is undesirable and if not detected causes the application to behave in strange and unusual ways.In some rare programming scenariosthis overflow is not only acceptable but is also desired.
The CLR offer IL instructions that allows the compiler to chose the desire bhaviour.The CLR has an instruction called add that adds to values together.The add instruction performs no overflow checking.The CLR also has an instruction called add.ovf that also add two values together. However add.ovf theows a System.OverflowException if an overflow occur.CLR also has similar IL instruction for Subtraction,multiplication and data conversion.
C# allows the programmer to decide how overflows should be handled.By default, overflow checking is turned off. This means that comipler generate IL code by using the versions to add that don't include overflow checking. As a result the code run faster but developer must be assured that overflow won't occur .
One way to get the C# complier to control overflow is to use the /Checked+ compiler switch. This switch tell the comipler to generate code that has the overflow checking versions of add.
Rather than have overflow checking turned on or off globally, programmers are much more likely to want to decide case by case whether to have overflow checking.C# allow this flexibility by offering checked and unchecked operators.
Byte b = 100;
b = checked(Byte(b+200)); // overflow exception is throw
or
checked
{
Byte b =100;
b += 200;
}
}
