'this' Keyword in C#

This is what this means

this is a common keyword that shows up in different programming languages, and sometimes the differences are subtle (and confusing!).

In C#, this can be referring to two different things, depending on the context in which it’s used.

this in a class

If you see this referenced in a class, chances are that it is a reference to the instance of the class. As an example:

class ThisKeyword
{
    public string MyFavoriteColor { get; set; } = "green";

    void AFunction()
    {
        var capture = this.MyFavoriteColor;
    }
}

In the above example, the capture variable will equal “green”. You are not required to use the this keyword here, it is implied. However, if you have a naming conflict in your class, you will be required to use it. Consider the following example:

class ThisKeyword
{
    public string MyFavoriteColor { get; set; } = "green";

    public void Test()
    {
        var MyFavoriteColor = "blue";

        //This will write out "blue".
        Console.WriteLine(MyFavoriteColor);

        //This will write out "green".
        Console.WriteLine(this.MyFavoriteColor);

        Console.ReadKey();
    }
}

this in extension methods

There is another place that you’ll see the this keyword popup in C# – extension methods. Extension methods are a form of monkey patching. Consider the following example:

class ThisKeyword
{
    public void APublicMethod()
    {
        //something
    }
}

static class ThisKeywordExtensions
{
    public static void ExtensionMethod(this ThisKeyword instance)
    {
        instance.APublicMethod();
    }
}

In the above example, this refers to the instance of ThisKeyword that is being “monkey patched” with the extension method.