Attempting to change inkcanvas pen size using slider C# XAML

Question

I have a slider with values 1-10. and an inkCanvas with default height and width of 1px. I am attempting to change the height and width based on the value of the slider. This is what I have tried but it gave me this error: " Object reference not set to an instance of an object ". What does this error mean?

edit: included xaml code:

Answer 1

I think you must have code inside penSizeSlider_ValueChanged to change the penSizes.SelectedValue . So you need either to just remove Value="1" part from <Slider..../> in your XAML code and set the value in code behind, as that will trigger the penSizeSlider_ValueChanged event before you have chance to initialize your penSize comboBox (as you only set Items of penSize in Window_Loaded event). Or you can initialize penSize.Items in XAML instead of in the code behind. and try again.

So you need to:

1. remove Value="1" part from <Slider..../> in your XAML

2. change Window_Loaded to:

    private void Window_Loaded (object sender, RoutedEventArgs e) { for (var i = 1; i <= 10; i++) { penSizes.Items.Add(i); } penSizes.SelectedIndex = 0; //set slider's value here penSizeSlider.Value=1; //...rest code }

PS: It would be better to just set a breakpoint and debug by yourself.

Answer 2

The error means that somewhere in your code, you're working with an object that still hasn't been initialized. Try to debug to find out which one.