Crear secciones personalizadas en el archivo de configuración

Are you tired of seeing your configuration settings as an endless list of key value pairs?

<add key="key0" value="value0" />
<add key="key1" value="value1" /> 
<add key="key2" value="value2" />
... 

Would you rather see something more like this?

<MySetting
  fileName="c:\temp"
  password="pencil"
  someOtherSetting="value" />

Join the club. Not only is the first approach prone to typos (AppSettings["tire"]or AppSettings["tier] anyone?), too many of these things all bunched together can cause your eyes to glaze over. It is a lot easier to manage when settings are grouped in logical bunches.

A while back Craig Andera solved this problem with the Last Configuration Section Handler he’d ever need. This basically made it easy to specify a custom strongly typed class to represent a logical group of settings using Xml Serialization. It led to a much cleaner configuration file.

But that was then and this is now. With ASP.NET 2.0, there’s an even easier waywhich I didn’t know about until Jeff Atwood recently turned me on to it.

So here is a quick run through in three easy steps.

Step one - Define your Custom Configuration Class

In this case, we’ll define a class to hold settings for a blog engine. We just need to define our class, inherit from System.Configuration.ConfigurationSection, and add a property per setting we wish to store.

using System;
using System.Configuration;

public class BlogSettings : ConfigurationSection
{
  private static BlogSettings settings 
    = ConfigurationManager.GetSection("BlogSettings") as BlogSettings;
        
  public static BlogSettings Settings
  {
    get
    {
      return settings;
    }
  }

  [ConfigurationProperty("frontPagePostCount"
    , DefaultValue = 20
    , IsRequired = false)]
  [IntegerValidator(MinValue = 1
    , MaxValue = 100)]
  public int FrontPagePostCount
  {
      get { return (int)this["frontPagePostCount"]; }
        set { this["frontPagePostCount"] = value; }
  }


  [ConfigurationProperty("title"
    , IsRequired=true)]
  [StringValidator(InvalidCharacters = "  ~!@#$%^&*()[]{}/;’\"|\\"
    , MinLength=1
    , MaxLength=256)]
  public string Title
  {
    get { return (string)this["title"]; }
    set { this["title"] = value; }
  }
}

Notice that you use an indexed property to store and retrieve each property value.

I also added a static property named Settings for convenience.

Step 2 - Add your new configuration section to web.config (or app.config).

<configuration>
  <configSections>
      <section name="BlogSettings" type="Fully.Qualified.TypeName.BlogSettings,   
      AssemblyName" />
  </configSections>
  <BlogSettings
    frontPagePostCount="10"
    title="You’ve Been Haacked" />
</configuration>

Step 3 - Enjoy your new custom configuration section

string title = BlogSettings.Settings.Title;
Response.Write(title); //it works!!!

What I covered is just a very brief overview to get you a taste of what is available in the Configuration API. I wrote more about configuration in the book I’m cowriting with Jeff Atwood, Jon Galloway, and K. Scott Allen.

If you want to get a more comprehensive overview and the nitty gritty, I recommend reading Unraveling the Mysteries of .NET 2.0 Configuration by Jon Rista.