Example
public interface ILogger
{
void Log(string message);
}
[Export(typeof(ILogger))]
[ExportMetadata("Name", "Console")]
public class ConsoleLogger:ILogger
{
public void Log(string message)
{
Console.WriteLine(message);
}
}
[Export(typeof(ILogger))]
[ExportMetadata("Name", "File")]
public class FileLogger:ILogger
{
public void Log(string message)
{
//Write the message to file
}
}
public class User
{
private readonly ILogger logger;
public User(ILogger logger)
{
this.logger = logger;
}
public void LogUser(string message)
{
logger.Log(message) ;
}
}
public interface ILoggerMetaData
{
string Name { get; }
}
internal class Program
{
private CompositionContainer _container;
[ImportMany]
private IEnumerable<Lazy<ILogger, ILoggerMetaData>> _loggers;
private static void Main()
{
ComposeLoggers();
Lazy<ILogger, ILoggerMetaData> loggerNameAndLoggerMapping = _ loggers.First((n) => ((n.Metadata.Name.ToUpper() =="Console"));
ILogger logger= loggerNameAndLoggerMapping.Value
var user = new User(logger);
user.LogUser("user name");
}
private void ComposeLoggers()
{
//An aggregate catalog that combines multiple catalogs
var catalog = new AggregateCatalog();
string loggersDllDirectory =Path.Combine(Utilities.GetApplicationDirectory(), "Loggers");
if (!Directory.Exists(loggersDllDirectory ))
{
Directory.CreateDirectory(loggersDllDirectory );
}
//Adds all the parts found in the same assembly as the PluginManager class
catalog.Catalogs.Add(new AssemblyCatalog(typeof(Program).Assembly));
catalog.Catalogs.Add(new DirectoryCatalog(loggersDllDirectory ));
//Create the CompositionContainer with the parts in the catalog
_container = new CompositionContainer(catalog);
//Fill the imports of this object
try
{
this._container.ComposeParts(this);
}
catch (CompositionException compositionException)
{
throw new CompositionException(compositionException.Message);
}
}
}
