Handler 4

gistfile1.cs

public interface ISomeTextService { string DoSomething(); }
public class SomeTextService : ISomeTextService { public string DoSomething() { return string.Empty; } }
public interface ISomeHtmlService { string DoSomethingElse(); }
public class SomeHtmlService : ISomeHtmlService { public string DoSomethingElse() { return string.Empty; } }
public enum RenderType {Text, Html}

public interface IRenderer<T> { string Render(T obj); }

public class FooTextRenderer : IRenderer<Foo>
{
    private readonly ISomeTextService _someTextService;
    public FooTextRenderer(ISomeTextService someTextService) { _someTextService = someTextService; }

    public string Render(Foo foo)
    {
        return "this is a foo" + _someTextService.DoSomething();
    }
}

public class FooHtmlRenderer : IRenderer<Foo>
{
    private readonly ISomeHtmlService _someHtmlService;
    public FooHtmlRenderer(ISomeHtmlService someHtmlService) { _someHtmlService = someHtmlService; }

    public string Render(Foo foo)
    {
        return "this is a foo" + _someHtmlService.DoSomethingElse();
    }
}

public class Foo
{
    // foo domain logic
}