Question

i have one doubt in mind that….

1) we can call & access any static method or variable from any non static method but from static method we can not access any non static method or variable…..why.

2) but we can create a instance of any class from static method.

please tell me the reason to understand better answer of my question.

class Class1
{
    static int x=0;
    int w = 0;
    private static Class2 test()
    {
        w = 88; // give error because w is not a static member.
        test1(); // give error because test1() is not a static function.
        Class2 z = new Class2(); // here i am creating instance of class2
        return z;
    }

    private int test1()
    {
        x = 9;
        return x;
    }
}

class Class2
{

}

thanks

Answer 1

To understand the reason why you’d first have to understand the difference between a class and an actual object.
I can define a class like the following:

public class Car
{
  public string Brand {get; set;}
}

What i will be telling the compiler by this is what a Car would look like if i where to create such a thing. No Car is created at this point but the computer has an understanding of what a car is. We have given it a blueprint. This is called a class

Next i can go and actually create a car:

Car myCar = new Car();
myCar.Brand = "Ford";
Car otherCar = new Car();
otherCar.Brand = "BMW";

Now myCar contains an actual object and i told the computer it is a car. I also created another car in otherCar. These are both individual objects. and both have their own Name belonging to the object.

So now we have 2 objects but still only 1 class.

Now sometimes the need may arise for properties of methods that have some link to the concept Car but don’t require a specific Car to work on. in C# we can define such members using the static keyword.

We can add the following method to our class:

public static Car GetFirstCarEverBuild();

To actually find the first car that was ever build we do not need access to a specific car. we will try to find a car here but we don’t start out with one. so we mark it static. this also means that we have to access to Brand of the car since we have no object to get it from. The case might even be that no Car at all was ever created in wich case the method can just return Null. No car has ever existed and you don’t need one to find that out.

the same goes for static fields and properties:

public static Car firstCar;

This field can store 1 car and 1 only. no matter how many cars you create. it’s value is tied to the class and not the object. So if myCar will store a value in this field then otherCar can read this same value.

Consider the following example to sum it all up:

public class Car
{
  public static Car firstCar;

  public Car()
  {
    if (firstCar == null)
      firstCar = this;
  }

  public string Brand {get; set;}

  public static Car GetFirstCarEverBuild()
  {
    return firstCar;
  }
}