Here I am going to explain what the use of
checked and unchecked keyword in C#. Here I am taking the some content from MSDN
to explain about it. A checked context, arithmetic overflow raises an exception.
In an unchecked context, arithmetic overflow is ignored and the result is
truncated.
- Checked Specify checked context.
- unchecked Specify unchecked
context.
The following operations are affected by the
overflow checking:
- Expressions using the following
predefined operators on integral types:
++ — - (unary) + - * / - Explicit numeric conversions between
integral types.
The checked/unchecked compiler option lets you
specify checked or unchecked context for all integer arithmetic statements that
are not explicitly in the scope of a checked or unchecked keyword. Now I am
going to explain one by one.
Checked
The checked keyword is used to control
the overflow-checking context for integral-type arithmetic operations and
conversions. It can be used as an operator or a statement according to the
following forms.
The checked statement:
checked block
The statement block that contains the
expressions to be evaluated in a checked context.
The checked operator:
checked (expression)
The expression to be evaluated in a checked
context. Notice that the expression must be in parentheses ( ).
Unchecked
The unchecked keyword is used to
control the overflow-checking context for integral-type arithmetic operations
and conversions. It can be used as an operator or a statement according to the
following forms.
The unchecked statement :
unchecked block
The statement block that contains the
expressions to be evaluated in an unchecked context.
The unchecked operator :
unchecked (expression)
The expression to be evaluated in an unchecked
context. Notice that the expression must be in parentheses ( ).
Example
namespace
Checked_Unchecked
{
class Program
{
public short a =
30000;
public short b =
20000;
public short c;
public int Add()
{
try
{
c =
checked((short)(a
+ b));
}
catch (System.OverflowException
e)
{
System.Console.WriteLine(e.ToString());
}
return c;
}
public int Mul()
{
try
{
checked
{
c = (short)(a
* b);
}
}
catch (System.OverflowException
e)
{
System.Console.WriteLine(e.ToString());
}
return c;
}
public int
Add_Unchecked()
{
try
{
c =
unchecked((short)(a
+ b));
}
catch (System.OverflowException
e)
{
System.Console.WriteLine(e.ToString());
}
return c;
}
public int
Mul_Unchecked()
{
try
{
unchecked
{
c = (short)(a
* b);
}
}
catch (System.OverflowException
e)
{
System.Console.WriteLine(e.ToString());
}
return c;
}
static void
Main(string[] args)
{
Program p = new
Program();
// For checked
Console.WriteLine("Checked output value is: {0}",
p.Add());
Console.WriteLine("Checked output value is: {0}",
p.Mul());
// For Unchecked
Console.WriteLine("Checked output value is: {0}",
p.Add_Unchecked());
Console.WriteLine("Checked output value is: {0}",
p.Mul_Unchecked());
Console.ReadKey(true);
}
}
}
Output
![Image1.jpg]()