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

Question

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?

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Answer 1

'this' refers to an instance of a class. Static is initialized without instantiation and hence the static method cannot refer to an 'instance' that is not created.

Answer 2

I am not sure if this helps your problem, but I believe these two code snippets are equivalent:

MyStaticClass.foo();

and simply

foo();

will both call the foo() method in the MyStaticClass class, assuming you call foo() from inside MyStaticClass

Edit - The easiest way to remember the difference between a static class and a non-static class is to think of something like the Math class in java. You can call Math.abs(x); to get the absolute value of x, and it does not really make sense to instantiate a Math object, which is why Math is a static class.

Answer 3

By static methods you can write:

MyClass.static_method();

which there is nothing to do with any object instance (so you don't need this keyword).

Because static_method() works and doesn't need object instances for its job. static_method() doesn't know which object instance do you have, but it can change the behavior of all object instances:

MyClass a = new MyClass();
MyClass b = new MyClass();
MyClass.static_method("PRINTER");
a.display(); //print something
b.display(); //print something
MyClass.static_method("MONITOR");
a.display(); //display something on monitor
b.display(); //display something on monitor

In this case, static_method() changes the behavior of display() method in all object instances of MyClass.

Answer 4

The short answer for you will be: this refers to an instance of a class which is non existing in a static scope.

But please, look for a good book/class and try to understand basic object oriented concepts before going further on any object oriented programming language.

Answer 5

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.

Answer 6

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.