Question

In my application, depending on needs, Some TabPages will be added to a TabControl programatically. Each page will contain a ListView and two ListBoxes:

//Color Picker
var colorBox = new ListBox
{
    DataSource = Enum.GetValues(typeof (KnownColor)),
    Height = 40,
    Width = tabFiles.Width/3,
    Dock = DockStyle.Bottom
};

page.Controls.Add(colorBox);

//Style Picker
var styleBox = new ListBox
{
    DataSource = Enum.GetValues(typeof(SymbolType)),
    Height = 40,
    Width = tabFiles.Width / 3,
    Dock = DockStyle.Bottom
};

page.Controls.Add(styleBox);

Now later I want to send the selected color and symbol to another class using the code below, it compiles but at runtime it fires invalid cast. How can I fix this?

Color color = (Color)((ListBox)tabFiles.TabPages[i].Controls[1]).SelectedItem;
SymbolType symbol = (SymbolType)((ListBox)tabFiles.TabPages[i].Controls[2]).SelectedItem;

P.S: I know that color and symbol are added to page with index 1 and 2 respectivly.

Thanks.

Answer 1

You are getting a perfectly valid runtime exception. System.Drawing.KnownColor is an enum which you are casting to a System.Drawing.Color which is a struct, they are two very different types.

The hint is in your own code. You are setting the DataSource of your ListBox from an enumeration:

DataSource = Enum.GetValues(typeof (KnownColor))

If you cannot change your data source, I suggest you convert from KnownColor to Color before casting using the Color.FromKnownColor() method.