Different APIs for ImageSharp Metadata

ImageMetadata_const.cs

// Contains all properties all images have
public interface IImageProperties
{
    // Standard properties
    int Height { get; set; }

    int Width { get; set; }
    // -- end of standard
    
    // This holds the more flexible values
    IImageMetadata this[int key] { get; set; }
}

// Class with all base keys
public class MetaKey
{    
    public const int Artist = 2;
    
    public const int Date = 4;
}
// Example for derived keys
internal class SharedKeys
{
    public const int ColorSpace = 5001;
}
public class JpegKey : MetaKey
{
    public const int Compression = 1001;
    
    public static int ColorSpace { get { return SharedKeys.ColorSpace; } }
}
public class ExiffKey : MetaKey
{
    public const int Foo = 2001;
    
    public static int ColorSpace { get { return SharedKeys.ColorSpace; } }
}

// Shared interface for the different value structs
// The interface will however result in boxing and unboxing
public interface IImageMetadata
{
    int Key { get; }
    
    string Value { get; set; }
}

public struct StringImageMetadata : IImageMetadata
{
    private int key;
    private string value;
    
    public StringImageMetadata(int key, string value)
    {
      this.key = key;
      this.value = value;
    }
    
    public int Key => this.key;
    
    public string Value
    {
      get { return this.value; }
      set { this.value = value; }
    }
}

public struct IntImageMetadata : IImageMetadata
{
    private int key;
    private int value;
    
    public IntImageMetadata(int key, int value)
    {
      this.key = key;
      this.value = value;
    }
    
    public int Key => this.key;
    
    public string Value
    {
      get { return this.value.ToString("D"); }
      set { this.value = int.Parse(value); }
    }
}

// Usage
{
   IImageProperties properties = image.Properties;
   var artist = properties[MetaKey.Artist].Value;
   var colorspace = properties[JpegKey.Colorspace].Value;
}

ImageMetadata_enum.cs

// Contains all properties all images have
public interface IImageProperties
{
    // Standard properties
    int Height { get; set; }

    int Width { get; set; }
    // -- end of standard
    
    // This holds the more flexible values
    IImageMetadata this[MetaKey key] { get; set; }
}

// Either keys of all formats or just the more common ones
// Having all keys will make the type increase steadily till it becomes unusable
// Having more than one place breaks type-safety
public enum MetaKey
{
    FrameDelay,    
    RepeatCount,    
    Artist
}

// Shared interface for the different value structs
// The interface will however result in boxing and unboxing
public interface IImageMetadata
{
    MetaKey Key { get; }
    
    string Value { get; set; }
}

public struct StringImageMetadata : IImageMetadata
{
    private MetaKey key;
    private string value;
    
    public StringImageMetadata(MetaKey key, string value)
    {
      this.key = key;
      this.value = value;
    }
    
    public MetaKey Key => this.key;
    
    public string Value
    {
      get { return this.value; }
      set { this.value = value; }
    }
}

public struct IntImageMetadata : IImageMetadata
{
    private MetaKey key;
    private int value;
    
    public IntImageMetadata(MetaKey key, int value)
    {
      this.key = key;
      this.value = value;
    }
    
    public MetaKey Key => this.key;
    
    public string Value
    {
      get { return this.value.ToString("D"); }
      set { this.value = int.Parse(value); }
    }
}

// Usage
{
   IImageProperties properties = image.Properties;
   var artist = properties[MetaKey.Artist].Value;
}