Question

I’ve a Document class which has two overloads taking one parameter each (String and Stream). Why can’t I use the following code to initialize Document class using Generics?

    public abstract class PdfDocumentEditBaseService<T> : IDocumentEditService<T>

    public T Rotate(T file, int pageNumber, float angle)
    {
        Document document = new Document(file); // cannot convert from 'T' to 'Stream'
        document.Pages[pageNumber].Rotation = (RotationMode)angle;
        document.SavePage(pageNumber);
        return file;
    }

Answer 1

I see a few suggestions to require T to inherit from Stream. And that will work. But, if your T really is always a stream, why not just remove the generic parameter and build that class like this:

public abstract class PdfDocumentEditBaseService : IDocumentEditService
{
    public Stream Rotate(Stream file, int pageNumber, float angle)
    {
        Document document = new Document(file); 
        document.Pages[pageNumber].Rotation = (RotationMode)angle;
        document.SavePage(pageNumber);
        return file;
    }