Why keyword 'this' cannot be used in a static method?

c# this static-members

33,098

Solution 1

Because this points to an instance of the class, in the static method you don't have an instance.

The this keyword refers to the current instance of the class. Static member functions do not have a this pointer

You'll notice the definition of a static member is

Use the static modifier to declare a static member, which belongs to the type itself rather than to a specific object

Which is why this has nothing to point to.

Solution 2

this is an instance of the current object. With a static method, there is no current object, and as such, this doesn't exist. It's not really a constraint, but the entire point of a method being static.

Solution 3

this refers to the current instance of a class and can therefore be used only in instance methods. Static methods act on class level, where there are no instances. Hence, no this.

Solution 4

this refers to the current instance of the object. A static method is a method on the class. It is not an instance method and therefore using this inside a static method is meaningless.

Solution 5

I'm pretty sure this isn't limited to C# and it isn't a constraint, it's a logical situation. As @Yuriy correctly states, this refers to the current instance of a class, i.e. you've used new (or DI) to instantiate the class (created an instance of) and you need some way internally to refer to that instance, i.e. this object. A static method is called without instantiating the class, there is, in effect, no object created and as such you can't access properties of which this is one.

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33,098

Author by

airbai

Updated on October 14, 2020

Comments

airbai over 3 years

Why can't the keyword this be used in a static method? I am wondering why C# defines this constraint. What benefits can be gained by this constraint?

[Update]: Actually, this is a question I got in an interview. I do know the usage of 'static' and 'this', based on all your response, I guess I know a little of why the two can not be used together. That is, for static method is used to changed state or do something in a type level, but when you need to use 'this' means you want to change the state or do something in a instance level. In order to differentiate the state change of a type and the state change of an instance, then c# donot allow use 'this' in a static method. Am I right?
Muhammad Huzaifa almost 14 years

Please explain why there's no instance in a static method :)
Blub almost 14 years

Think about how you call static methods. Class.Method() like Animal.Eat() You never needed an instance (new Animal()) for calling the static method. That's why there is none.
strager almost 14 years

You're mixing C++ and C# here, I think.
jessegavin almost 14 years

I can't imagine a static animal, not to mention one that eats.
Monoman almost 14 years

Thanks jleedev for the formatting. Doesn't know how to do it, yet. :)
airbai almost 14 years

For 'this isn't limited to C# and it isn't a constraint, it's a logical situation', I agree : )