Dhananjay Kumar

Basics of C#: Checked and Unchecked Conversions

Objective

In this article, I will discuss about Checked and unchecked keyword and conversions in C#.

Consider the below code

Program.cs



using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication7
{
class Program
{
static void Main(string[] args)
{
int number = int.MaxValue;
number = number + 1;
Console.WriteLine(number);
Console.Read();


}
}
}

Now, if you see the above code

1. We are taking maximum integer value in a variable. And that is 2147483647.

2. We are increasing the number by 1. Now here it should get overflow because an integer variable cannot hold a number greater than 2147483647

So, now data will overflow and truncate during the assignment.

So, as the output we will get

If you notice above output, number assigned is truncated to –2147483647

It happened because compiler is doing unchecked compilation

So forcefully do the checked compilation, we will use CHECKED keyword. Just put all the codes in between checked block

So, now to avoid truncating during overflow assignment, we need to put our code in between Checked block.

So, modify the above code as below

Programs.cs

using System;

using System.Collections.Generic;



using System.Linq;
using System.Text;

namespace ConsoleApplication7
{
class Program
{
static void Main(string[] args)
{

checked
{
int number = int.MaxValue;
number = number + 1;
Console.WriteLine(number);
Console.Read();
}

}
}
}