c# - Button click event doesn't work properly

Question

This following code handle button click event. When the user click first time it sets the lable as "First Time", and when the user click second time it sets the lable as "Second Time". But it doesn't work properly. When I first click it, it sets the lable as "First time", which is correct, but when I click second time, nothing happend.

My code:

int counter=0;    
protected void btnCompTagUpdate_Click(object sender, EventArgs e)
{

    if (counter == 0)
    {
        lable1.Text="First Time";
        counter++;
    }
    else if (counter == 1)
    {
        lable1.Text="Second Time";
        counter--;
    }

    }

How can I fix it?

Answer 1

The values of instance fields like counter are not saved across postbacks. You need to store counter in ViewState, Session, or some other persistent store, whichever is more appropriate. For example:

private int Counter
{
    get { return ((int?)this.ViewState["Counter"]).GetValueOrDefault(); }
    set { this.ViewState["Counter"] = value; }
}

Then reference this.Counter instead of counter in btnCompTagUpdate_Click.