C# | this Keyword

this keyword is used to refer to the current instance of the class. It is used to access members from the constructors, instance methods, and instance accessors. this keyword is also used to track the instance which is invoked to perform some calculation or further processing related to that instance. Following are the different ways to use ‘this’ keyword in C# :
Program 1: Using ‘this’ keyword to refer current class instance members

csharp

// C# program for using 'this' keyword to
// refer current class instance members
using System;
namespace geeksforgeeks {

class Geeks {

    // instance member
    public string Name;

    public string GetName()
    {
        return Name;
    }


    public void SetName(string Name)
    {
         // referring to current instance
         //"this.Name" refers to class member
         this.Name = Name;
    }
}

class program {

    // Main Method
    public static void Main()
    {
        Geeks obj = new Geeks();
        obj.SetName("Geeksforgeeks");
        Console.WriteLine(obj.GetName());
    }
}
}

Output:

Geeksforgeeks

Program 2 : Using this() to invoke the constructor in same class

csharp

// C# program for using 'this' keyword to
// invoke the constructor in same class
using System;
namespace geeksforgeeks {

class Geeks {

    // calling another constructor
    // calls Geeks(string Name)
    // before Geeks()
    public Geeks() : this("geeks")
    {
        Console.WriteLine("Non-Parameter Constructor Called");
    }

    // Declare Parameter Constructor
    public Geeks(string Name)
    {
        Console.WriteLine("Parameter Constructor Called");
    }
}

class program {

    // Main Method
    public static void Main()
    {
            Geeks obj = new Geeks();
            // Warning: obj never used..
    }
}
}

Output:

Parameter Constructor Called
Non-Parameter Constructor Called

Program 3: Using ‘this’ keyword to invoke current class method 

csharp

// C# code for using this to invoke current
// class method
using System;
class Test {

    void display()
    {
        // calling function show()
        this.show();

        Console.WriteLine("Inside display function");
    }

    void show()
    {
        Console.WriteLine("Inside show function");
    }

    // Main Method
    public static void Main(String []args)
    {
        Test t1 = new Test();
        t1.display();
    }
}

Output

Inside show function
Inside display function

Program 4: Using ‘this’ keyword as method parameter 

csharp

// C# code for using 'this'
// keyword as method parameter
using System;
class Test
{
    int a;
    int b;

    // Default constructor
    Test()
    {
        a = 10;
        b = 20;
    }

    // Method that receives 'this'
    // keyword as parameter
    void display(Test obj)
    {
        Console.WriteLine("a = " + a + " b = " + b);
    }

    // Method that returns current
    // class instance
    void get()
    {
        display(this);
    }

    // Main Method
    public static void Main(String[] args)
    {
        Test obj = new Test();
        obj.get();
    }
}

Output:

a = 10 b = 20

Program 5: Using this keyword to declare an indexer 

csharp

// C# code for using 'this'
// keyword to declare indexer
using System;
namespace geeksforgeeks {

class Geeks {

    private string[] days = new string[7];

    // declaring an indexer
    public string this[int index]
    {
        get
        {
            return days[index];
        }

        set
        {
            days[index] = value;
        }
    }
}


class Program {

    // Main Method
    public static void Main()
    {
        Geeks g = new Geeks();
        g[0] = "Sun";
        g[1] = "Mon";
        g[2] = "Tue";
        g[3] = "Wed";
        g[4] = "Thu";
        g[5] = "Fri";
        g[6] = "Sat";
        for (int i = 0; i < 7; i++)
            Console.Write(g[i] + " ");
    }
}
}

Output:

Sun Mon Tue Wed Thu Fri Sat