gistfile1.txt

public interface IOption<T>:IEquatable<IOption<T>>,  IEquatable<T>
	{
		bool IsDefined
		{
			get;
		}
    // Something Method
    // ...
	}
  
  public struct InternalOption<T> : IOption<T>{
    // 様々なInterfaceの実装
    
		public override bool Equals (object obj)
		{
			var isOption = obj is IOption<T>;
			if (isOption)
				return Equals ((IOption<T>)obj);

			if(obj is T){
				return Equals ((T)obj);
			}
			return false;
		}
    /// ↓みたいな関数の実装
  	public static  bool operator ==(IOption<T> option, T t){
			if (option == null || t == null)
				return false;
			return option.Equals (t);
		}
  }