How to encapsulate 'global' variables in C#? /best practice

Question

In C# what is the best practice for encapsulating variables I need to use in multiple methods? Is it OK to simply declare them at the top of my class above the two methods?

Also if I am using app settings from my config file should I use a getter? like this...

private string mySetting{ get { return WebConfigurationManager.AppSettings["mySetting"]; } }

What best practice is?

Answer 1

It's not just OK. According to the book Clean Code it's actually a very good practice, and Uncle Bob really encourages it. A variable used by many methods could show a high degree of cohesion between the methods . Moreover, a high degree of object variables could also hint that said class should be split in two so declaring them as object variables could help you find out hidden class candidates.

Object level variables aren't global variables, so don't be afraid to use them if they should be shared by various methods.

Answer 2

Encapsulating your settings in a constant manner is a great idea.

What I do is create a settings class either one static global one or multiple instance classes which I'll then manage with dependency injection. Then I load all the settings from configuration into that class on start up.

I've also written a little library that makes use of reflection to make this even easier.

Once my settings are in my config file

<?xml version="1.0" encoding="utf-8" ?>
<configuration>   
    <appSettings>
        <add key="Domain" value="example.com" />
        <add key="PagingSize" value="30" />
        <add key="Invalid.C#.Identifier" value="test" />
    </appSettings>
</configuration>

I make a static or instance class depending on my needs. For simple applications with only a few settings one static class is fine.

private static class Settings
{
    public string Domain { get; set; }

    public int PagingSize { get; set; }

    [Named("Invalid.C#.Identifier")]
    public string ICID { get; set; }

}

Then using my library call either Inflate.Static or Inflate.Instance and the cool thing is I can use any key value source.

using Fire.Configuration;

Inflate.Static( typeof(Settings), x => ConfigurationManager.AppSettings[x] );

All the code for this is in GitHub at https://github.com/Enexure/Enexure.Fire.Configuration

There is even a nuget package:

PM> Install-Package Enexure.Fire.Configuration

Code for reference:

using System;
using System.Linq;
using System.Reflection;
using Fire.Extensions;

namespace Fire.Configuration
{
    public static class Inflate
    {
        public static void Static( Type type, Func<string, string> dictionary )
        {
            Fill( null, type, dictionary );
        }

        public static void Instance( object instance, Func<string, string> dictionary )
        {
            Fill( instance, instance.GetType(), dictionary );
        }


        private static void Fill( object instance, Type type, Func<string, string> dictionary ) 
        {

            PropertyInfo[] properties;
            if (instance == null) {

                // Static
                properties = type.GetProperties( BindingFlags.Public | BindingFlags.Static | BindingFlags.DeclaredOnly );
            } else {

                // Instance
                properties = type.GetProperties( BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly );
            }

            // Get app settings and convert
            foreach (PropertyInfo property in properties) {
                var attributes = property.GetCustomAttributes( true );
                if (!attributes.Any( x => x is Ignore )) {

                    var named = attributes.FirstOrDefault( x => x is Named ) as Named;

                    var value = dictionary((named != null)? named.Name : property.Name);

                    object result;
                    if (ExtendConversion.ConvertTo(value, property.PropertyType, out result)) {
                        property.SetValue( instance, result, null );
                    }
                }
            }
        }
    }
}