Essential Object Oriented Programming concepts for Selenium C# (static, non-static)

Essential​​ Object Oriented Programming concepts in C#

What are​​ Static & Non-Static functions​​ in C Sharp?

  • Create a new project

  • Give the project name as OOPS

 

  • Right click Program.cs​​ 

 

  • Click Rename​​ and​​ rename it to Static_NonStatic

 

  • Hit enter,​​ the class name should now be changed to Static_NonStatic​​ 

 

  • As​​ you can see​​ above,​​ the main function is a static function​​ because it has the static keyword associated with it.​​ We​​ can also make your own static functions.​​ 

 

  • The​​ sum() function below is static since it has static keyword associated with it

 

  • We​​ can also make non-static functions, example, sendEmail() function below, it does NOT have static keyword associated with it

 

  • So there are 2 types off functions: static and non-static

What are local variables?

  • We​​ can​​ also have​​ local variables inside a static and non-static function. The life/scope of these local​​ variables is only inside the function they are defined​​ 

What are global variables?

  • Global variables are present inside the​​ class but outside the functions​​ viz they are present parallel to the functions inside the class, generally declared at the top of the class, at the very beginning of the class.

 

  • Global variables can be used across all the functions​​ with some conditions. If global variables satisfy those conditions than they can be used across all the functions inside the class.

 

  • Let us define a non-static​​ Global​​ variable (line 12)

 

  • Let us define a static​​ Global​​ variable ‘age’​​ (line 13)

 

  • In summary, we have:
    2 types of functions: static and non-static
    2 types of variables: local and global
    2 types of global variables: static and non-static

  • The local variables are​​ neither​​ static​​ nor​​ non-static.​​ If you try to make a local variable static, you will see an​​ error

Some rules

  • Static function can only access the static stuff​​ (static global variables, static functions):

    Since sum() is a static function, therefore it can be called​​ 
    inside the static main function (line 17)


    But​​ 
    we will get an error if we​​ call sendEmail() function inside static​​ main function, since sendEmail() function is​​ non-static​​ (line 18)


Similarly the static variable age can be accessed inside static main function​​ (line 19)


However​​ 
we​​ will get an error if​​ we​​ try to access non-static name variable​​ ‘name’​​ inside static main function​​ (line 20)

 

  • There is no rule associated with non-static stuff:
    Look at lines 33-35, we are able to access static and non-static stuff inside non-static function​​ sendEmail()

 

  • How can we access non-static stuff inside​​ static​​ Main​​ function? To understand this, lets create a class​​ name Car​​ (right click project >Add >New Item)




 

  • Let​​ us make the Car class public

 

  • Now what all a Car can do? It can start, it can accelerate etc.​​ So let​​ us create 2 non-static functions​​ inside the Car class: start() and accelerate()

 

  • Let​​ us also create a static​​ Main function​​ 

 

  • Now Car will have some properties like: model, price, wheels. So let​​ us define global variables of Car class

 

  • Now inside the Main function we can create the object of a class. To do that, we can use the keyword​​ new​​ followed by the classname

 

  • As soon as an object is created,​​ a memory location gets associated with this object.​​ Inside this object, all the​​ non-static​​ stuff will be residing

 

  • Let us create 3 Car objects, so 3 locations are assigned in the memory, each location having non-static stuff

  • We can also say​​ Car c1 = new Car()
    Note:​​ ‘new Car()’ is the actual object, c1 is the reference​​ pointing​​ towards​​ the​​ new​​ object​​ Car​​ (c1​​ is not the object)



  • Now just type​​ c1.​​ You will see all the non static stuff associated with this object​​ [example, model, price, start() etc]

 

  • So we can access​​ the​​ non-static​​ stuff​​ inside the static​​ Main function​​ only​​ by creating an​​ object​​ of the class, not otherwise​​ ​​ 

 

  • Notice line 26​​ below. We are trying to access non-static start() function directly inside the static Main function, hence getting an error (we saw this while discussing rules)​​ 

  • Similarly we can create another object​​ and​​ assign the properties (non-static stuff)

 

  • Let us now try to print the models of both the cars​​ (lines 25, 34)
    ​​ 

 

  • In a project,​​ we can have only 1 Main function. Right now we have​​ 2​​ Main function:​​ in Car.cs​​ and in​​ Static_NonStatic.cs
    T
    o execute the Main function of Car.cs class, we can either comment the Main function in Static_NonStatic.cs class or​​ double click ‘Properties’ (seen under Project on RHS) and​​ select OOPS.Car from​​ the ‘Startup object’ dropdown

 

  • Save the changes​​ and run the project,​​ notice that models are printed in​​ the o/p

Similarly we can print other properties as well.

Thank you for reading!

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