enumerable2.cs

public interface IStringReader
{
	IEnumerable<string> GetStrings();
}

public class InMemoryStringReader : IStringReader
{
	private readonly string[] _strings;
	
	public InMemoryStringReader(string[] strings)
	{
		_strings = strings;
	}

	public IEnumerable<string> GetStrings()
	{
		return _strings;
	}
}

public class NetworkStringReader : IStringReader
{
	private readonly TcpClient _client;
	private readonly StreamReader _reader;
	
	public NetworkStringReader(TcpClient client)
	{
		_client = client;
		_reader = new StreamReader(client.GetStream());
	}
	
	public IEnumerable<string> GetStrings()
	{
		yield return _reader.ReadLine();
	}
}