Understand unsafe block and low level programming in C#

Understand unsafe block and low level programming in C#

If you have programming experience in C or C++ then probably you know the concept of low level programming. In low level programming we can directly talk with system hardware. For example we can control the process or can allocate memory according to our need. For this low level features C and C family language is used to control various hardware. In C++ also we can get the test of low level programming. Now, we all know that C# is high level object oriented programming language, but in spite of high level language, it has few low level features. We can write low level code in C# programming language. In this article we will see how to do that.

To write low level code we have to know two things. The first one is “All low level code should place within unsafe block”

The structure of unsafe block

unsafe{
}

And the second one is “We have to allow compiler to compile unsafe code” . Here is the setting in VisualStudio.

Go to project’s property->Go to “Build” option->Check the allow unsafe checkbook. Here is screenshot of settings.

Now compile will allow writing low level code in .NET application using C#. So, let’s start with few examples.  Have a look on below code.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApp
{
   class Program
    {
      
        static void Main(string[] args)
        {
            unsafe
            {
                int a =100;
                int* p = &a;
                Console.WriteLine("Value of a is :- " + *p);
            }
            Console.ReadLine();
        }
    }
}

In this example we have define one unsafe block at first and within unsafe block we have define one integer variable and another integer pointer. The beauty of integer pointer is , it can able to store the address of integer variable. We are storing the address of variable a within integer pointer by below code.

Int *p = &a;

The ‘&’ operator is called address of operator, which returns address of any variable. Then within Console.WriteLine() function we are printing the value of variable ‘a’ with the help of pointer ‘p’ .Note that to get the value of specific pointer we are using “*” operator, which is nothing but “value at the address operator”.

Here is output

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Diagnostics;
using System.Threading;
namespace ConsoleApp
{
   class Program
    {
        static void Main(string[] args)
        {
            unsafe
            {
                int a = 200;
                int* p = &a;
                Console.WriteLine("Address of a is:- " + (int)p);
            }
            Console.ReadLine();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Diagnostics;
using System.Threading;
namespace ConsoleApp
{
   class Program
    {
       unsafe public static void Print(int* pa)
       {
           for (int* ip = pa; ip < (pa + 5); ip++)
           {
               Console.WriteLine("value {0} at the address: {1}", *ip, (int)ip);
           }
       }
 
        static void Main(string[] args)
        {
            unsafe
            {
                //Allocate memory on stack
                int* p = stackalloc int[5];
                //Set Value into memory
                p[0] = 10;
                p[1] = 20;
                p[2] = 30;
                p[3] = 40;
                p[4] = 50;
                Print(p);
            }
            Console.ReadLine();
        }
    }
}