"If is class" Condition Failing

Hi I have 3 base interfaces:

public interface IKlarfDefect
{
    int TEST { get; set; }
    int DEFECTID { get; set; }

}

public interface IKlarfDefect <TImageListInfo> : IKlarfDefect
{

    List<TImageListInfo> KlarfImageList { get; set; }
}

public interface IHasKlarfImageList<TImageListInfo>
{
    List<TImageListInfo> KlarfImageList { get; }
}

These classes implement it:

public class CIMKlarfDefect : IKlarfDefect, IHasKlarfImageList<CIMKlarfImageListInfo>
{
    public int TEST { get; set; }
    public int DEFECTID { get; set; }

    public List<CIMKlarfImageListInfo> KlarfImageList { get; set; } = new List<CIMKlarfImageListInfo>();
    
}

public class RMTKlarfDefect : IKlarfDefect, IHasKlarfImageList<CIMKlarfImageListInfo>
{
    public int TEST { get; set; }
    public int DEFECTID { get; set; }
    
    public List<RMTKlarfImageListInfo> KlarfImageList { get; set; } = new List<RMTKlarfImageListInfo>();
}

Then I have this function in another class that tries to read through these classes:

internal static string CreateCIMDefectListString(IEnumerable<IKlarfDefect<IKlarfImageListInfo>> klarfDefectList)
{
    StringBuilder defectListString = new StringBuilder();
    defectListString.AppendLine("");
    foreach (var klarfDefect in klarfDefectList) { 
        defectListString.Append(klarfDefect.TEST).Append(" ");
        defectListString.Append(klarfDefect.DEFECTID).Append(" ");
        
        if (klarfDefect is IHasKlarfImageList<IKlarfImageListInfo> grcKlarfDefect) 
        {
            if (grcKlarfDefect.KlarfImageList.Count == 0)
            {
                defectListString.Append("N;");
                defectListString.AppendLine();
            }
            
        }
    }
    return defectListString.ToString();

}

It compiles but the if statement fails when I am passing in either RMTKlarfDefect or CIMKlarfDefect. Might anyone know why this is?

if klarfDefect is IHasKlarfImageList grcKlarfDefect
fails as in, it doesn’t return true which would allow it to process the imagelist

>Solution :

Your if statement says

if (klarfDefect is IHasKlarfImageList<IKlarfImageListInfo> grcKlarfDefect)

But your classes implement

IHasKlarfImageList<CIMKlarfImageListInfo>

So you need to update your if statement accordingly:

 if (klarfDefect is IHasKlarfImageList<CIMKlarfImageListInfo> grcKlarfDefect)