Question

Is it possible to define an interface where one of the objects is a list of another interface?

I have two EF objects:

=====

class ImageType1
{
    string Id
    string Name
    List<ImageType1Size> Sizes
}

class ImageType1Size
{
    string Id
    int Width
    int Height
}

class ImageType2
{
    string UserId
    string ImageId
    string Name
    List<ImageType2Size> Sizes
}

class ImageType2Size
{
    string UserId
    string ImageId
    int Width
    int Height
}

=====

For each of the image size classes, all of the properties are keys (just a side note).

Now, what I want to do is create the following two interfaces:

=====

interface IImage
{
    string Name
    List<ImageSize> Sizes
}

interface IImageSize
{
    int Width
    int Height
}

=====

In my project, I have created partials for ImageType1, ImageType1Size, ImageType2, and ImageType2Size, each using the respective interface.

I’m getting an error in trying to cast the Sizes property in ImageType1 and ImageType2 to use the interface IImageSize.

=====

Is this possible to do? If I’m not clear please let me know and I’ll rephrase the question.

Thanks!

Answer 1

You might want to consider generics here:

interface IImage<TSize> where TSize : IImageSize
{
    List<TSize> Sizes { get; }
}

class ImageType1 : IImage<ImageType1Size>
{
    List<ImageType1Size> Sizes { get; private set; }
}

Alternatively, this would work:

interface IImage
{
    IEnumerable<IImageSize> Sizes { get; }
}

class ImageType1
{
    public List<ImageType1Size> SizeList { get; private set; }

    public IEnumerable<IImageSize> Sizes { get { return SizeList; } }
}

It depends on what works best for how you operate on the data.