This Keyword

Inside the class body this refers to the current class object.

It can be used to access / modify members and call functions inside the class.

Example

using System;

namespace ConsoleApp1
{
    class Rectangle
    {
        private double width;
        private double height;

public void setWidth(double width)
        {
            // Modify object's member:
            this.width = width;
        }

public void setHeight(double height)
        {
            // Modify object's member:
            this.height = height;
        }

public double calcArea()
        {
            // Access class members:
            return this.height * this.width;
        }

public void printData()
        {
            Console.WriteLine("Width = " + this.width);
            Console.WriteLine("Height = " + this.height);

// Access class function:
            double area = this.calcArea();
            Console.WriteLine("Area = " + area);
        }
    }

class Program
    {
        static void Main(string[] args)
        {
            Rectangle rectangle = new Rectangle();

rectangle.setWidth(3);
            rectangle.setHeight(2);

rectangle.printData();
        }
    }
}

Output:

Explanation:

At lines 13, 19 values are set to the members width and height.
At lines 25, 30 and 31 members are accessed.
At line 34 a class function is called.
At line 43 an object is created.
At lines 45 and 46 in which width and height are set, this points to the object created at line 43.