Same Variable, different result

Question

I just started out learning c# and I came across something confusing, I hope someone can explain it to me :)

namespace WindowsFormsApplication4
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        int Md = 0;

        private void cmdAnzeigen1_Click(object sender, EventArgs e)
        {
            int x = 0;
            Md = Md + 1;
            x = x + 1;
            lblErgebnis.Text = "x: " + x + "\n" + "Gx:" + Md;       
        }
    }
}

How come Md always increases by 1, but x doesn't (stays at 1)? I don't understand, they are both the same variables.

Answer 1

Md is an instance variable, declared outside any method. It's part of the state of the object, so it "lives" (and maintains its value) for as long as the object is "alive". Different instances of Form1 would have independent Md variables.

x is a local variable - there's a new variable every time you call the method, and it always starts with a value of 0.

If that isn't enough explanation, please consult a good introductory C# book or tutorial - explaining everything about variables would be a bit much for Stack Overflow, which is more for handling specific problems than learning the fundamentals of a programming language.