Question

I have this error:

Cannot implicitly convert type
‘System.Collections.Generic.List’ to
‘System.Collections.Generic.List’

For the following piece of code:

When I try to add to the list:

if (information != null) // not empty
{
    foreach (CharacterInformation info in information)
    {
        chButtons.Add(new GuiSelectCharacterButton(
            selectGui,
            new Rectangle(100, 100, 450, 100)
        ));
        chButtons[chButtons.Count - 1].ImageTexture = GUISprites.Instance().GetTexture(UITexture.RainbowDash);
        chButtons[chButtons.Count - 1].Texture = GUISprites.Instance().GetTexture(UITexture.CommonButtonNotPressed);
        chButtons[chButtons.Count - 1].PressedTexture = GUISprites.Instance().GetTexture(UITexture.CommonButtonPressed);
        chButtons[chButtons.Count - 1].ImageTextureWidth = 90;
        chButtons[chButtons.Count - 1].ImageTextureHeight = 90;
        chButtons[chButtons.Count - 1].ButtonPressed += LoginCharacterHandler;
        chButtons[chButtons.Count - 1].Font = GameFonts.Instance().GetSpriteFont(FontType.UI);
        chButtons[chButtons.Count - 1].Information = information[chButtons.Count - 1];
    }
}
// error at this line
buttoncontainer.ButtonList = chButtons;

Class declaration:

public class GuiSelectCharacterButton : GUIImageButton, IGameUserInterfaceImageButton
{
    public GuiSelectCharacterButton(GUI parent, Rectangle area)
        : base(parent, area)
    {

    }
}

Interface:

public interface IGameUserInterfaceImageButton : IGameUserInterfaceComponent
{
    bool InsideContainer { get; set; }
    Rectangle InsideContainerArea { get; set; }
}

List of IGameUserInterfaceImageButton:

private List<IGameUserInterfaceImageButton> buttonList;

public List<IGameUserInterfaceImageButton> ButtonList
{
    get
    {
        return buttonList;
    }
    set
    {
        buttonList = value;
        scrollbarThumbTotalHeight = marginButtons;
        scrollbarThumbY = 0;
        int yhelper = 0;
        foreach (IGameUserInterfaceImageButton button in buttonList)
        {
            yhelper += marginButtons;
            button.InsideContainer = true;
            button.InsideContainerArea = new Rectangle(
                marginXbutton,
                yhelper,
                button.Area.Width,
                button.Area.Height
            );
            yhelper += marginButtons + button.Area.Height;
            scrollbarThumbTotalHeight += button.Area.Height + marginButtons * 2;
        }
        scrollbarThumbDrawHeight = 0;
        if (scrollbarThumbTotalHeight > Area.Height)
        {
            scrollbarThumbDrawHeight = (int)Math.Pow(AreaScrollbar.Height, 2) / scrollbarThumbTotalHeight;
        }
    }
}

I don’t know where my mistake is. The base class (GUIImageButton) implements everything of said interface. I did this on other parts of my program but for any weird reason it doesn’t work here.

Answer 1

You can’t cast directly from List<A> to List<IA> event when A inherits from IA.

What you can do is make chButtons also of type IGameUserInterfaceImageButton. Then cast each item to the interface, as you add them:

var chButtons = new List<IGameUserInterfaceImageButton>();
chButtons.Add(
    (IGameUserInterfaceImageButton)new GuiSelectCharacterButton(
        // etc ...
    )
);
// this is now valid
buttoncontainer.ButtonList = chButtons