gistfile1.cs

public class MainEntryPointClass : BaseClass
{
  private ILogic Logic;
  private IFileLogger FileLogger;

  public MainEntryPointClass () : this(new Logic())
  {
  }

  public IFileLogger FileLogger { get; set; }    // For property injection for TDD or (e.g.) AutoFac
  public ILogic Logic { get; set; }

  public SetupProperties()
  {
     this.ConfigProperties.Add(typeof(string), "DirectoryPath", "C:\\");
  }

  public Run()
  {
    ConstructConditionalDependencies(this.ConfigProperties.Find("DirectoryPath").Value());

    this.Logic.RandomProperty = this.ConfigProperties.Find(..).Value();
  }

  private void ConstructConditionalDependencies(string directoryPath)
  {
    // FileLogger
    if (this.FileLogger == null) {
      this.FileLogger = new FileLogger(directoryPath);
    }

    // Logic (which needs FileLogger)
    if (this.Logic == null)
    {
      this.Logic = new Logic(new Timer(), this.FileLogger);
    }
  }
}


/// From this point downwards we're all good clean DI + ctor injection.
public class Logic : ILogic
{
   private ITimer Timer;
   private ILogger Logger;

   public class Logic(ITimer timer, ILogger logger)
   {
       this.Timer = timer;
       this.Logger = logger;
   }

   public SomeMethod()
   {
      this.Logger.Write("Data");  /******* How does DirectoryPath get assigned? *******/
   }
}

public interface IFileLogger
{
    void WriteData(string data);        
}

 public class FileLogger : IFileLogger
{
    public FileLogger(string directoryPath)
   {
     this.DirectoryPath = directoryPath;
    }

    public void WriteData(string data)
    {
    }

    public string DirectoryPath { get; private set; }
}