Is `this` keyword optional when accessing members in C#?

Question

I notice that if you have a private member in a class, you can access it in the class methods by just referring to it\'s name. You do not need to say this.memberName

Answer 1

"This" is almost always optional when you call members of current class.

However, it is used for other purposes, e.g. to pass the current class instance as a parameter or to set a property,field or variable to the current instance.

The only case where you must use it to call a method is when you call an extension method:

class AClass {
    void CallIt() {
        Test();                     //not valid
        this.Test();                //valid 
    }
}
static class AnExtension {
    public static void Test(this AClass source) {

    }
}