CODEWITHSUNDEEP
c#interface
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Reputation: 321

C# Add extended interface to list

I'm currently trying to add a collection of interfaces to another collection - the problem is, i only want the extended interface, and not the parent.

Let me elaborate:

interface IScanner
{
    void scan();
}

interface IPhotocopier : IScanner
{
     void Copy();
}

public class PrintingBusiness
{
    List<IPhotocopier> Photocopiers { get; set; }
}

public class ScannerBusiness
{
    List<IScanner> Scanners { get; set; }
}

public class Program
{   
      static void Main(string[] args)
      {
            PrintingBusiness printerBusiness = new PrintingBusiness();
            printerBusiness.Photocopiers = new List<IPhotocopier>();
            printerBusiness.Photocopiers.Add(new HPPrinter());
            printerBusiness.Photocopiers.Add(new CanonPrinter())

            ScannerBusiness scannerBusiness = new ScannerBusiness();
            scannerBusiness.Scanners = new List<IScanner>();
            scannerBusiness.Scanners.Add(printerBusiness.Photocopiers); // Here i want to retreive all the IScanners from my Photocopiers collection, but i get an ArgumentError: Cannot Convert from List<IPhotocopier> to List<IScanner>. 

      }
}

I want to access the collection of IScanner interfaces from my Photocopiers collection - i thought i could do it directly by simply adding the Photocopiers collection to my Scanners collection - but to i need to iterate over each Photocopier and cast to IScanner and then add them to my Scanners collection? :-)

Upvotes: 0

Views: 54

Answers (1)

Patrick Hofman
Patrick Hofman

Reputation: 156978

You should use the AddRange method, since that can iterate over the Photocopiers list and add all those items to the Scanners list:

scannerBusiness.Scanners.AddRange(printerBusiness.Photocopiers);

You won't need any conversion since the IPhotocopier instances can implicitly be casted to IScanner.

Also, don't forget to initialize your lists. They are null now.

Upvotes: 3

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