CSharp - Type Creation Deconstructors

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Introduction

A deconstructor assigns fields back to a set of variables.

A deconstruction method must be called Deconstruct, and have one or more out parameters.

The following code create a Rectangle class with Deconstruct method 

class Rectangle
{
     public readonly float Width, Height;

     public Rectangle (float width, float height)
     {
         Width = width;
         Height = height;
     }

     public void Deconstruct (out float width, out float height)
     {
         width = Width;
         height = Height;
     }
}

To call the deconstructor: 

var rect = new Rectangle (3, 4);
(float width, float height) = rect;          // Deconstruction
Console.WriteLine (width + " " + height);    // 3 4

The second line is the deconstructing call which is equivalent to the following: 

float width, height;
rect.Deconstruct (out width, out height);

Or: 

rect.Deconstruct (out var width, out var height);

Deconstructing calls allow implicit typing: 

(var width, var height) = rect;

Or simply: 

var (width, height) = rect;

If the variables into which you're deconstructing are already defined, omit the types: 

float width, height;
(width, height) = rect;

This is called a deconstructing assignment.

You can overload the Deconstruct method and return different value to caller.

Demo

using System;
class MainClass/*from   ww w. j  a  v  a 2s .c  o m*/
{
   public static void Main(string[] args)
   {

        var rect = new Rectangle (3, 4);
        (float width, float height) = rect;          // Deconstruction
        Console.WriteLine (width + " " + height);    // 3 4

   }
}
class Rectangle
{
     public readonly float Width, Height;

     public Rectangle (float width, float height)
     {
         Width = width;
         Height = height;
     }

     public void Deconstruct (out float width, out float height)
     {
         width = Width;
         height = Height;
     }
}

Result