What is the use of static variable in C#? When to use it? Why can't I declare the static variable inside method?

A static variable shares the value of it among all instances of the class.

Example without declaring it static

public  class Variable
{
    public int i = 5;
    public void test()
    {
        i=i+5;
        Console.WriteLine(i);
    }
}


public class Exercise
{
    static void Main()
    {
        Variable var = new Variable();
        var.test();
        Variable var1 = new Variable();
        var1.test();
        Console.ReadKey();
    }
}
Explanation:If you look at the above example i just declare int variable.when i run this code the output will be 10 and 10.Its simple

Now Lets Look at the static variable Here,I am declaring the variable as a static.

Example with static variable

public  class Variable
{
    public static int i = 5;
    public void test()
    {
        i=i+5;
        Console.WriteLine(i);
    }
}


public class Exercise
{
    static void Main()
    {
        Variable var = new Variable();
        var.test();
        Variable var1 = new Variable();
        var1.test();
        Console.ReadKey();
    }
}
Now when I run above code then the output will be 10 and 15. So static variable value is shared among all instances of that class.