feature: define tracing - log time

[aoancea]

This decorator is going to support the logging of time taken by a method from a class to execute, thus, I define the following interface and its implementation:

public interface IFoo
{
    string Bar(string text);
}

public class Foo : IFoo
{
    public string Bar(string text)
    {
        return text;
    }
}

Before I can talk about the decorator, a mechanism is needed to provide access to data, and more exactly to the elapsed time. For this I define the following interface:

public interface ILogger
{
    void Log(Stopwatch sw);
}

Given the above interfaces, I define the following decorator:

public class Foo_Time_Decorator : IFoo
{
    private readonly IFoo decorated;
    private readonly ILogger logger;

    public Foo_Time_Decorator(IFoo decorated, ILogger logger)
    {
        this.decorated = decorated;
        this.logger = logger;
    }

    public string Bar(string text)
    {
        Stopwatch sw = new Stopwatch();
        sw.Start();

        string result = decorated.Bar(text);

        sw.Stop();

        logger.Log(sw);

        return result;
    }
}

Usage example:

public class ConsoleLogger : ILogger
{
    public void Log(Stopwatch sw)
    {
        Console.WriteLine(sw.ElapsedMilliseconds);
    }
}

class Program
{
    static void(string args)
    {
        IFoo foo = new Foo();
        ILogger logger = new ConsoleLogger();
        IFoo fooDecorator = new Foo_Time_Decorator(foo, logger);

        fooDecorator.Bar("some text");
    }
}

When running a console application, the ElapsedMilliseconds would be displayed in the console.

Note: The wiring of objects will be done using a DI container.