Dependency injection with a static logger, static helper class

Question

I have a static class which calls a static Logger class,

e.g

static class DoesStuffStatic {   public static void DoStuff()   {     try     {       //something     }     catch(Exception e)     {       //do stuff;        Logger.Log(e);     }   } }  static class Logger {   public static void Log(Exception e)   {      //do stuff here   } } 

How do I inject the Logger into my static class?

Note: I've read Dependency Injection in .NET with examples?, but this seems to use an instance logger.

Answer 1

This is not necessarily so. As long as your static logger exposes a method for:

• Injection of the classes you WANT injected, or
• Injection of the DI Container in an appropriate method call prior to running it (say in something like the asp.net global.asax Application_Start method), then you should be fine.

Here's an example. Take the following class for DI:

 public class Logger : ILogger     {         public void Log(string stringToLog)         {            Console.WriteLine(stringToLog);         }     }      public interface ILogger     {         void Log(string stringToLog);     } 

And here's our static class which needs a logger:

public static class SomeStaticClass     {         private static IKernel _diContainer;         private static ILogger _logger;          public static void Init(IKernel dIcontainer)         {             _diContainer = dIcontainer;             _logger = _diContainer.Get<ILogger>();         }           public static void Log(string stringToLog)         {             _logger.Log(stringToLog);         }       } 

Now, in a global startup for your app (in this case, in my global.asax.cs), you can instantiate your DI Container, then hand that off to your static class.

public class Global : Ninject.Web.NinjectHttpApplication     {          protected override IKernel CreateKernel()         {             return Container;         }           static IKernel Container         {             get             {                 var standardKernel = new StandardKernel();                 standardKernel.Bind<ILogger>().To<Logger>();                 return standardKernel;             }          }          void Application_Start(object sender, EventArgs e)         {             SomeStaticClass.Init(Container);             SomeStaticClass.Log("Dependency Injection with Statics is totally possible");          } 

And presto! You are now up and running with DI in your static classes.

Hope that helps someone. I am re-working an application which uses a LOT of static classes, and we've been using this successfully for a while now.