Static keyword

Static means something which cannot be instantiated(We cannot create instance). We cannot create an object of a static class and cannot access static members using an object. Static keyword can be used before classes, variables, methods, properties, operators, events and constructors.

NOTE
If static keyword present before class, we cannot create instance of that class and also if its a static class all the members that we going to define inside must be static one. If static keyword present before any member of the class, the only way to access those static members is by directly calling the className.memberName


CODE

EG 1 . Creating sample class with static field and method, non static field and method.

class Program {
    static void Main() {
        //The only way to access static member is by directly calling className.MemberName
        sampleClass.field1 = 1;
        Console.WriteLine(sampleClass.method1());

        //The only way to access non static member is by creating new instance
        sampleClass s1 = new sampleClass();
        s1.field2 = 1;
        Console.WriteLine(s1.method2());
    }
}
class sampleClass {
    public static double field1;
    public double field2;
    public static string method1() {
        return "This is static method";
    }
    public string method2() {
        return "This is non static method";
    }
}

OUTPUT
This is static method
This is non static method

CODE EXPLANATION
In the above code, we created a class called sampleClass, inside that we created a static field called field1 and a static method called method1(). We also defined a nonstatic field called field2 and a non-static method called method2(). The members what we defined as static can only be accessed by directly calling the className.methodName whereas the members what we defined as non static can only be accessed by creating new instance of that class(instanceName.memberName)


Where to use static class?
Static classes are useful and provide an easy way to access its members that does not need to work differently for different objects. The static Math class contains methods like pow(), sqrt(), sin(), etc... performs mathematical operations, here these Math class methods are not going to work differently for different objects hence it is static method. In simple terms, if we are going to create class just to create methods which perform simple operations like converting degree to radian, converting celsius to fahrenheit etc, then we can go with static class.
Suppose if we want to create a game that has hundreds of enemies and each of them has fields like health, ammo, and methods like shoot() and run(). With OOP we can create a single Enemy class with required fields and methods. Then, we can create multiple enemy objects from it. Each of the enemy objects will have its own version of health and ammo fields. And, they can use the common shoot() and run() methods. In this case we need go with non-static class.

Exercises
1. Create a class with 5 static methods and 5 non static methods and invoke all methods inside main().


(Click Here, For more exercises)