Differences between checked and unchecked

The maximum value of the int type is 2147483647. the sum of the two maximum values exceeds the maximum value of the int type, that is, overflow occurs.

 
ClassProgram
 
 
{
 
 
Static VoidMain (String[] ARGs)
 
{
 
 
IntY = 2147483647;
 
 
IntX = 2147483647;
 
 
IntZ = x + y;
 
 
 
Console. writeline (Z. tostring ());
 
 
Console. readkey ();
 
 
}
 
 
}
 
 
 

Place the breakpoint in int z = x + y. The code line and one-step debugging show that the value of Z is-2. Because the maximum value of the int type is 2147483647, x + y exceeds the maximum value, and overflow occurs.

 

□Use checked

If we want the compiler to help us determine whether it is overflow, we will use the checked keyword.

 
ClassProgram
 
 
{
 
 
Static VoidMain (String[] ARGs)
 
 
{
 
IntY = 2147483647;
 
 
IntX = 2147483647;
 
 
IntZ =Checked(X + y );
 
 
}
 
}
 

Run and throw an overflow exception:

 

If we want to manually capture and print exceptions, we should write as follows:

 
ClassProgram
 
 
{
 
 
Static VoidMain (String[] ARGs)
 
{
 
 
IntY = 2147483647;
 
 
IntX = 2147483647;
 
 
 
 
Try
 
{
 
 
IntZ =Checked(X + y );
 
 
}
 
 
Catch(Overflowexception ex)
 
{
 
 
Console. writeline (ex. Message );
 
 
}
 
 
Console. readkey ();
 
 
}
 
}
 
 
 

Run,

 

□Use unchecked

Using unchecked will not throw an overflow exception.

 
ClassProgram
 
 
{
 
Static VoidMain (String[] ARGs)
 
 
{
 
 
IntY = 2147483647;
 
 
IntX = 2147483647;
 
IntZ =Unchecked(X + y );
 
 
 
 
Console. writeline (Z. tostring ());
 
 
Console. readkey ();
 
 
}
 
}
 
 
 

Result:-2

 

Conclusion: The checked keyword is used to check and capture overflow exceptions. The unchecked keyword is used to ignore overflow exceptions.