1public interface IDocument
2{
3    void Open();
4    void Save();
5}
6
7public class TextDocument : IDocument
8{
9    public void Open()
10    {
11        Console.WriteLine("Opening a text document.");
12    }
13
14    public void Save()
15    {
16        Console.WriteLine("Saving a text document.");
17    }
18}
19
20public class PdfDocument : IDocument
21{
22    public void Open()
23    {
24        Console.WriteLine("Opening a PDF document.");
25    }
26
27    public void Save()
28    {
29        Console.WriteLine("Saving a PDF document.");
30    }
31}
32
33public class HtmlDocument : IDocument
34{
35    public void Open()
36    {
37        Console.WriteLine("Opening an HTML document.");
38    }
39
40    public void Save()
41    {
42        Console.WriteLine("Saving an HTML document.");
43    }
44}

1public abstract class DocumentCreator
2{
3    public abstract IDocument CreateDocument();
4
5    public void ProcessDocument()
6    {
7        IDocument document = CreateDocument();
8        document.Open();
9        document.Save();
10    }
11}
12
13public class TextDocumentCreator : DocumentCreator
14{
15    public override IDocument CreateDocument()
16    {
17        return new TextDocument();
18    }
19}
20
21public class PdfDocumentCreator : DocumentCreator
22{
23    public override IDocument CreateDocument()
24    {
25        return new PdfDocument();
26    }
27}
28
29public class HtmlDocumentCreator : DocumentCreator
30{
31    public override IDocument CreateDocument()
32    {
33        return new HtmlDocument();
34    }
35}

1public class Program
2{
3    public static void Main()
4    {
5        DocumentCreator creator = new TextDocumentCreator();
6        creator.ProcessDocument();
7
8        creator = new PdfDocumentCreator();
9        creator.ProcessDocument();
10
11        creator = new HtmlDocumentCreator();
12        creator.ProcessDocument();
13    }
14}

Opening a text document.
Saving a text document.
Opening a PDF document.
Saving a PDF document.
Opening an HTML document.
Saving an HTML document.