Question

OutputFormatsBase is base class for managing Output Formats. OutputFormats1 and OutputFormats2 classes are inherited from OutputFormatsBase class.

I have the problem with static variable _listOfObjects which is in OutputFormatsBase class and can’t find a way to solve it.

If I make _listOfObjects static everything works fine except that OutputFormats1 and OutputFormats2 classes static instances are shared, not good.

Could anyone suggest how to solve this? I completely lost.

public class OutputFormats1 : OutputFormatsBase
{
    public static readonly OutputFormats1 Bmp = new OutputFormats1 { Value = "BMP", FileExtension = "bmp", Id = 1 };
    public static readonly OutputFormats1 Jpg = new OutputFormats1 { Value = "JPG", FileExtension = "jpg", Id = 2 };
    public static readonly OutputFormats1 Png = new OutputFormats1 { Value = "PNG", FileExtension = "png", Id = 3 };
    public static readonly OutputFormats1 Tiff = new OutputFormats1 { Value = "TIFF", FileExtension = "tif", Id = 4 };
    public override OutputFormatsBase Selected { get; set; }
    public override OutputFormatsBase Default
    {
        get { return Png; }
    }
}

public class OutputFormats2 : OutputFormatsBase
{
    public static readonly OutputFormats2 Pdf = new OutputFormats2 { Value = "PDF", FileExtension = "pdf", Id = 1 };
    public override OutputFormatsBase Selected { get; set; }
    public override OutputFormatsBase Default
    {
        get { return Pdf; }
    }
}

public abstract class OutputFormatsBase
{
     private static readonly List<OutputFormatsBase> _listOfObjects = new List<OutputFormatsBase>();
     public string Value { get; protected internal set; }
     public string FileExtension { get; protected internal set; }
     public int Id { get; protected internal set; }

     public abstract OutputFormatsBase Selected { get; set; }
     public abstract OutputFormatsBase Default { get; }


     protected OutputFormatsBase()
     {
         _listOfObjects.Add(this);
     }


     public bool Validate(string format)
     {
         for (var i = 0; i < _listOfObjects.Count - 1; i++)
         {
             var outputFormats = _listOfObjects[i];
             if (format.ToLower() == outputFormats.Value.ToLower())
             {
                 Selected = outputFormats;
                 return true;
             }
         }
         return false;
     }
 }

Answer 1

You could try something like that :

public abstract class OutputFormatsBase<T> where T : OutputFormatsBase
{
 private static readonly List<T> _listOfObjects = new List<T>();

 protected OutputFormatsBase()
 {
  _listOfObjects.Add((T)this);
 }
}

You’ll have one instance of _listOfObjects per template instanciation.