C# | Deconstructors with Tuples

28 Aug, 2019
A tuple is a data structure which gives you the easiest way to represent a data set which has multiple values that may/may not be related to each other. But if you are trying to retrieve multiple fields or property values from the tuple is more difficult. So, to overcome this problem deconstructor was introduced in C# 7.0. It is used to divide the variable values or tuple into parts and assigns those values to the new variables. It also used with classes and structures. Here we only discuss the working of deconstructor with tuples.
In Tuples, deconstructor is used to divide a tuple into parts and assign these parts individually into new variables. So, you can access an individual field or property value. You can deconstruct a tuple in four different ways:
1. You can deconstruct a tuple simply by explicitly declare the type of each field inside the parentheses. But you are not allowed to specify a specific type outside the parentheses even every field in the tuple is of the same type. If you try to do, then you will get an error.
Example:
// C# program to illustrate the concept // of deconstruction with the tupleusing System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;  namespace ConsoleApp1 {  class GFG {      // This method returns the Pet details    public(string, string, int, int, string) PetDetails(string type,                      string name, int height, int age, string color)    {        string p_type = type;        string p_name = name;        int p_height = height;        int p_age = age;        string p_color = color;        return (p_type, p_name, p_height, p_height, p_color);    }      // Main method    static void Main(string[] args)    {          // Creating object of GFG class        GFG g = new GFG();          // Deconstruct the given tuple        // So that we can directly access individual fields        // By explicitly declaring types        (string type, string name, int height, int age, string color) = g.PetDetails("Dog",                                                                 "Dollar", 124, 3, "White");        Console.WriteLine("Pet Details:");        Console.WriteLine("Type: " + type);        Console.WriteLine("Name: " + name);        Console.WriteLine("Height: " + height);        Console.WriteLine("Age: " + age);        Console.WriteLine("Color: " + color);        Console.ReadLine();    }}}
Output:
2. You can deconstruct a tuple by using var keyword so that C# infers the type of each variable. You can use the var keyword in two different ways:
You are allowed to place the var keyword outside of the parentheses.
You are allowed to place the var keyword individually inside the parentheses with some or all variables.
Example:
// C# program to illustrate the concept // of deconstruction with the tupleusing System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;  namespace ConsoleApp1 {  class GFG {      // This method returns the Pet details    public(string, string, int, int, string) PetDetails(string type,                      string name, int height, int age, string color)    {        string p_type = type;        string p_name = name;        int p_height = height;        int p_age = age;        string p_color = color;        return (p_type, p_name, p_height, p_height, p_color);    }      // Main method    static void Main(string[] args)    {          // Creating object of GFG class        GFG g = new GFG();          // Deconstruct the given tuple        // So that we can directly         // access individual fields        // Using var keyword        var(type1, name1, height1, age1, color1) = g.PetDetails("Dog",                                           "Dollar", 124, 3, "White");        Console.WriteLine("Pet Details:");        Console.WriteLine("Type: " + type1);        Console.WriteLine("Name: " + name1);        Console.WriteLine("Height: " + height1);        Console.WriteLine("Age: " + age1);        Console.WriteLine("Color: " + color1);          (var type2, var name2, var height2, var age2, var color2) = g.PetDetails("Cat",                                                          "Poo", 104, 1, "Black&White");        Console.WriteLine("\nPet Details:");        Console.WriteLine("Type: " + type2);        Console.WriteLine("Name: " + name2);        Console.WriteLine("Height: " + height2);        Console.WriteLine("Age: " + age2);        Console.WriteLine("Color: " + color2);        Console.ReadLine();    }}}
Output:
3. You can deconstruct a tuple into a variable that are already declared. As shown in the below example:
Example:
// C# program to illustrate the concept // of deconstruction with the tupleusing System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;  namespace ConsoleApp1 {  class GFG {      // This method returns the Pet details    public(string, string, int, int, string) PetDetails(string type,                      string name, int height, int age, string color)    {        string p_type = type;        string p_name = name;        int p_height = height;        int p_age = age;        string p_color = color;        return (p_type, p_name, p_height, p_height, p_color);    }      // Main method    static void Main(string[] args)    {          // Creating object of GFG class        GFG g = new GFG();          // Declaring and initializing variables        string type = "Cow";        string name = "BooBoo";        int height = 234;        int age = 4;        string color = "Black&white";          // Deconstruct the given tuple        // So that we can directly         // access individual fields        // By declaring variables        (type, name, height, age, color) = g.PetDetails("Cat",                                       "Mew", 105, 2, "Brown");        Console.WriteLine("Pet Details:");        Console.WriteLine("Type: " + type);        Console.WriteLine("Name: " + name);        Console.WriteLine("Height: " + height);        Console.WriteLine("Age: " + age);        Console.WriteLine("Color: " + color);        Console.ReadLine();    }}}
Output:
4. You can also use discards in deconstruction. Discards are write-only variables whose values are meant to be ignored. And discards are designated by using an underscore character (“_”) in an assignment. You are allowed to discard as many values as you want and all are represented by the single discard, _.
Syntax:
(var1, _, var3, _, var5) = method_name(var1_values, var2_values, var3_value, var4_values, var5_value);
Example:
// C# program to illustrate the concept// of deconstruction with tupleusing System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;  namespace ConsoleApp1 {  class GFG {      // This method returns     // the Pet details    public(string, string, int, int, string) PetDetails(string type,                     string name, int height, int age, string color)    {        string p_type = type;        string p_name = name;        int p_height = height;        int p_age = age;        string p_color = color;        return (p_type, p_name, p_height, p_height, p_color);    }      // Main method    static void Main(string[] args)    {          // Creating object of GFG class        GFG g = new GFG();          // Discarding field values        // in deconstruction          (string type, _, int height, _, string color) = g.PetDetails("Dog",                                                "Dollar", 124, 3, "White");        Console.WriteLine("Pet Details:");        Console.WriteLine("Type: " + type);        Console.WriteLine("Height: " + height);        Console.WriteLine("Color: " + color);        Console.ReadLine();    }}}
Output:
Note: In deconstruction, you need to assign each element to a variable if you eliminate any element, then the compiler will give an error. And you are not allowed to mix declarations and assignments to existing variables on the left-hand side of a deconstruction if you eliminate any element, then the compiler will give an error.
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