Object composition

void Main()
{
    IDocumentLoaderModule[] modules = new IDocumentLoaderModule[]
    {
        new IntDocumentLoaderModule(),
        new StringDocumentLoaderModule()
    };

    DocumentLoader loader = new DocumentLoader(modules);

    Document document = loader.LoadDocument();

    document.Dump();
}

public class DocumentLoader
{
    private readonly IReadOnlyList<IDocumentLoaderModule> _modules;

    public DocumentLoader(IReadOnlyList<IDocumentLoaderModule> modules)
    {
        _modules = modules;
    }

    public Document LoadDocument()
    {
        Document document = new Document();

        foreach (var module in _modules)
            module.Load(document);

        return document;
    }
}

public class Document
{
    public int IntValue { get; set; }
    public string StringValue { get; set; }
}

public interface IDocumentLoaderModule
{
    void Load(Document document);
}

public class IntDocumentLoaderModule : IDocumentLoaderModule
{
    public void Load (Document document)
    {
        // some logic
        document.IntValue = 42;
    }
}

public class StringDocumentLoaderModule : IDocumentLoaderModule
{
    public void Load (Document document)
    {
        // some logic
        document.StringValue = "Foo";
    }
}