using System;

using System.Collections.Generic;           

​

public class ProductDto {

​

}

​

public class AlbumDto<T> where T : TrackDto

{

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    private ICollection<T> _tracks = new List<T>();

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    public ICollection<T> Tracks

    {

        get { return _tracks; }

        set { _tracks = value ?? new List<T>(); }

    }

​

}

​

public class AudioAlbumDto : AlbumDto<AudioTrackDto>

{

}

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public class AudioVideoAlbumDto : AlbumDto<TrackDto>

{

}

​

public class VideoAlbumDto : AlbumDto<VideoTrackDto>

{

}

​

public class HRAudioAlbumDto : AlbumDto<HQTrackDto> { }

​

​

public class TrackDto

{

    public string Title { get; set; }

    public int TrackNumber { get; set; }

}

​

public class HQTrackDto : TrackDto { }

​

public class AudioTrackDto : TrackDto { }

​

public class VideoTrackDto : TrackDto { }