Question

I’m creating two separate classes for accessing a custom file. Let’s call my classes MyReader and MyWriter.

I’m following the same pattern that .NET classes such as StreamReader and StreamWriter follow, where there is a separate class for reading and writing. In addition to following an established pattern, this also solved some other problems for me.

However, I really need a few common settings for both the reader and writer classes. For example, I have a delimiter character that the user should be able to change. I also have some fixed data that contains common information used for parsing.

Could someone suggest a good pattern, especially one that follows common .NET framework practices, for creating common settings for multiple classes like this? My classes already inherit from a .NET class. Seems like multiple inheritance might have been one way but doesn’t seem supported in C#.

(I’m using Visual Studio 2012.)

Answer 1

This seems to be one of those rare instances where a Singleton might make good sense:

public abstract class MyBase
{
    // This is the .NET class you're inheriting from, just putting it as a placeholder.
}

public class MyReader : MyBase
{
    private static readonly IMySettings settings = MySettings.Instance;
}

public class MyWriter : MyBase
{
    private static readonly IMySettings settings = MySettings.Instance;
}

internal interface IMySettings
{
    // Define your setting's properties, such as delimiter character.
}

internal sealed class MySettings : IMySettings
{
    private MySettings()
    {
    }

    public static IMySettings Instance
    {
        get
        {
            return Nested.Instance;
        }
    }

    // Implement your setting's properties, such as delimiter character.

    private static class Nested
    {
        private static readonly IMySettings instance = new MySettings();

        // Explicit static constructor to tell C# compiler not to mark type as beforefieldinit
        static Nested()
        {
        }

        public static IMySettings Instance
        {
            get
            {
                return instance;
            }
        }
    }
}

Hope this helps.