Single responsability example, step 3

FileLoader.cs

class FileLoader : IFileLoader
{
    public Stream Load(string fileName)
    { 
        return new FileStream(fileName, FileMode.Open); 
    }
}

ProductRepository.cs

class ProductRepository : IProductRepository
{
    private readonly IFileLoader loader; 

    public ProductRepository()
    {
        loader = new FileLoader(); 
    }

    public IEnumerable<Product> GetByFileName(string fileName)
    {
        var products = new List<Product>(); 
        using (Stream input = loader.Load(fileName))
        {
            var reader = XmlReader.Create(input);
            while (reader.Read())
            {
                if (reader.Name != "product") continue;
                var product = new Product();
                product.Id = int.Parse(reader.GetAttribute("id"));
                product.Name = reader.GetAttribute("name");
                product.UnitPrice = decimal.Parse(reader.GetAttribute("unitPrice"));
                product.Discontinued = bool.Parse(reader.GetAttribute("discontinued"));
                products.Add(product);
            }
        }
        return products;
    }
}