DecoratorPattern.cs

using System;
using System.Collections.Concurrent;

public class Program
{
	public static void Main()
	{
		ILogger logger = new ConsoleLogger();
		IServicePartitionResolver servicePartitionResolver = new ServicePartitionResolver();
		servicePartitionResolver = new ResilientServicePartitionResolver(servicePartitionResolver, 3);
		servicePartitionResolver = new CachingServicePartitionResolver(servicePartitionResolver);
		servicePartitionResolver = new LoggingServicePartitionResolver(servicePartitionResolver, logger);
		logger.Log(servicePartitionResolver.ResolveServicePartition(new Uri("http://www.google.com")));
	}
}

public interface IServicePartitionResolver
{
	string ResolveServicePartition(Uri serviceURI);
}

public class ServicePartitionResolver : IServicePartitionResolver
{
	public string ResolveServicePartition(Uri serviceURI)
	{
		return serviceURI.ToString();
	}
}

public class ResilientServicePartitionResolver : IServicePartitionResolver
{
	IServicePartitionResolver servicePartitionResolver;
	int retryCount;
	
	public ResilientServicePartitionResolver(IServicePartitionResolver servicePartitionResolver, int retryCount = 1)
	{
		this.servicePartitionResolver = servicePartitionResolver;
		this.retryCount = retryCount;
	}

	public string ResolveServicePartition(Uri serviceURI)
	{
		int currentAttempt = 0;
		while (true)
		{
			try
			{
				return this.servicePartitionResolver.ResolveServicePartition(serviceURI);
			}
			catch (Exception)
			{
				if (currentAttempt <= this.retryCount)
				{
					continue;
				}

				throw;
			}
		}
	}
}

public interface ILogger
{
	void Log(string message);
	void LogError(Exception ex);
}

public class ConsoleLogger : ILogger
{
	public void Log(string message)
	{
		Console.WriteLine(message);
	}

	public void LogError(Exception ex)
	{
		Console.Error.WriteLine(ex.Message);
	}
}

public class LoggingServicePartitionResolver : IServicePartitionResolver
{
	IServicePartitionResolver servicePartitionResolver;
	ILogger logger;
	
	public LoggingServicePartitionResolver(IServicePartitionResolver servicePartitionResolver, ILogger logger)
	{
		this.servicePartitionResolver = servicePartitionResolver;
		this.logger = logger;
	}

	public string ResolveServicePartition(Uri serviceURI)
	{
		this.logger.Log($"{nameof(IServicePartitionResolver)}.{nameof(ResolveServicePartition)}({nameof(serviceURI)}: {serviceURI})");
		try
		{
			return this.servicePartitionResolver.ResolveServicePartition(serviceURI);
		}
		catch (Exception ex)
		{
			this.logger.LogError(ex);
			throw;
		}
	}
}

public class CachingServicePartitionResolver : IServicePartitionResolver
{
	IServicePartitionResolver servicePartitionResolver;
	ConcurrentDictionary<Uri, string> cache;
	
	public CachingServicePartitionResolver(IServicePartitionResolver servicePartitionResolver)
	{
		this.servicePartitionResolver = servicePartitionResolver;
		this.cache = new ConcurrentDictionary<Uri, string>();
	}

	public string ResolveServicePartition(Uri serviceURI)
	{
		return this.cache.GetOrAdd(serviceURI, (uri) => this.servicePartitionResolver.ResolveServicePartition(uri));
	}
}