Using and Dispose in C#

Use of dispose and using in C# managed and unmanaged classes.

Introduction

Simple example of how using <using> keyword in our C# code and what is required to implement correctly in our classes.

Let's introduce the problem

Let's suppose we have a class:

public class myclass
    {
        public int? x { get; set; }
        public string text { get; set; }

        public myclass()
        {
            x = 0;
            text = string.Empty;
        }

        public void myset()
        {
            x = 100;
            text = "test";
            Console.WriteLine($"x={x}, text={text}");
        }
    }

and we want to use in our program. Let's say for example:

static void Main(string[] args)
  {
      myclass x = new myclass();
      x.myset();
  }    

When program will finish the memory allocated will be freed by using garbage collector mechanism.

This is true for managed code (code managed by CLR) (here) but for unmanaged code a destructor should be implemented.

Let's introduce using

The using statement is used to perform optimzation in memory allocation and helps to perform clean-up activities (here). Following our example, the code could be something like this:

  using (myclass c = new myclass()) //<== ERROR: myclass does not implements IDisposable interface.
  {
      c.myset();
  }

🔴 Yes, in order to use correctly using statement the class is required to use IDisposable interface, and then to implement Dispose() method. Our class then will be something like ths:

public class myclass:IDisposable
    {
        public int? x { get; set; }
        public string text { get; set; }

        public myclass()
        {
            x = 0;
            text = string.Empty;
        }

        public void myset()
        {
            x = 100;
            text = "test";
            Console.WriteLine($"x={x}, text={text}");
        }
        
        public void Dispose()
        {
            x = null;
            text = null;
            Console.WriteLine("Disposed.");
        }
    }

🔵 Finally, our main program will be something like this:

    using (myclass c = new myclass())
    {                                       //<== Here cnt is invoked
        c.myset();                          //<== Here myset method is invoked
    }                                       //<== Here Dispose is invoked

Release notes

Code example on how to use using statement and use of IDisposable interface. More details in the project.