Question

my application is Windows Forms (VS2010 C#); I set a double variable at the beginning of the form as:

private double Wwidth;

Then I change the its value when I open a file:

 Wwidth = image.WindowWidth;

The value of Wwdith equals 265.0. When I select a trackbar,

private void tbrWidth_Scroll(object sender, System.EventArgs e)
        {
            double newWidth = tbrWidth.Value;
            double wd = Wwidth - newWidth;
...}

the value of Wwdith changes to 0.0?

Any suggestions. Thanks in advance.

Answer 1

Variables don’t change themselves. So there are two possibilities:

1. some bit of code you’ve forgotten about changed it
2. it is a different instance

To rule out 2, you could put (in the two places):

Debug.WriteLine(
    System.Runtime.CompilerServices.RuntimeHelpers.GetHashCode(this));

If you get the same number printed from both places, you’re probably still in the same instance. To rule out 1 – change it and put a break-point in:

private double _wwidth;
private double Wwidth {
    get { return _wwidth; }
    set { _wwidth = value; } // <==== put a breakpoint here
}

Now you should stop automatically at any code that is changing the value