C# Keywords Tutorial Part 83: this

In C#, the this keyword refers to the current instance of the class. It can be used to access instance members such as fields, properties, and methods. In this blog post, we will discuss how to use the this keyword in C# with some code examples.

Using the this keyword to Access Instance Members

One of the most common uses of the this keyword is to access instance members. Here’s an example:

public class Person
{
    private string name;

    public Person(string name)
    {
        this.name = name;
    }

    public void SayHello()
    {
        Console.WriteLine("Hello, my name is " + this.name + ".");
    }
}

In this example, the Person class has a private field name and a constructor that takes a name parameter. The SayHello method uses the this keyword to access the name field and print a greeting that includes the name.

Using the this Keyword to Avoid Naming Conflicts

Another use of the this keyword is to avoid naming conflicts between class members and method parameters or local variables. Here’s an example:

public class Calculator
{
    private int result;

    public Calculator(int result)
    {
        this.result = result;
    }

    public void Add(int result)
    {
        this.result += result;
    }

    public int GetResult()
    {
        return this.result;
    }
}

In this example, the Calculator class has a private field result and a constructor that takes a result parameter. The Add method also takes a result parameter, which is added to the result field using the this keyword to disambiguate between the two. The GetResult method returns the value of the result field.

Using the this Keyword in Extension Methods

Extension methods allow you to add functionality to existing classes without modifying their source code. You can use the this keyword in an extension method to indicate that the method is an extension method. Here’s an example:

public static class StringExtensions
{
    public static string Reverse(this string str)
    {
        char[] chars = str.ToCharArray();
        Array.Reverse(chars);
        return new string(chars);
    }
}

In this example, the StringExtensions class has a static Reverse method that takes a string parameter and returns the reversed string. The method is marked with the this keyword to indicate that it is an extension method for the string class.