Creating Custom Configuration Sections in Web.config

Most ASP.Net web applications have some amount of configuration. In ASP.Net you can add configuration settings to the Web.config under the <appSettings> section. Here’s an example:

    <add key="name" value="Mike" />  

Configuration settings can be retrieved as follows:


If you only have a handful of settings, <appSettings> is convenient and easy. However, there is no schema to enforce compliance and specifying collections is awkward. It also quickly becomes unwieldy as the number of settings grows. I’ve seen projects resort to naming conventions to keep things orderly. There’s a better way.

Custom configuration sections allow for a more rigorous specification of configuration settings and can include default and required values. IntelliSense support is also enabled. Here’s an example of my blog configuration.

  title="Mike Ward's Technology Blog"   
  description=".Net, Technology, Life, Whatever... "   
  copyright="Copyright (c) 2013 Mike Ward - All rights reserved"   
  timezone="Eastern Standard Time"   
  dateformat="MMMM d, yyyy"   
    <add id="0" title=".Net" description="Microsoft .Net Technlogies" />  
    <add id="1" title="ASP.Net" description="Microsoft ASP.Net Technlogies" />  
    <add id="2" title="Bloget" description="My ASP Webforms Blog Control" />  
    <add id="3" title="Browser" description="Browser related (all browsers)" />  
    <add id="4" title="C#" description="Microsoft's C# Language" />  
    <add id="5" title="Freebies" description="You know you want it" />  
    <add id="6" title="Life" description="Because there's more to life than programming (I think)" />  
    <add id="7" title="Applications" description="Desktop applications are so 90's" />  
    <add id="8" title="Programming" description="General programming topics" />  
    <add id="9" title="Security" description="It's an illusion" />  
    <add id="10" title="Technology" description="Gadgets, cars, etc." />  
    <add id="11" title="Science" description="Bubble, gurgle, boil..." />  
    <add id="12" title="PC Tips" description="How to use that F@#$ing thing" />  
    <add id="13" title="Desktop Gadgets" description="Something I really miss about in Windows" />  
    <add id="14" title="Links" description="Links to stuff I find interesting" />  
    <add id="15" title="Naughty &amp; Nice" description="Feed back about buying from vendors" />  
    <add id="16" title="F#" description="Microsoft's very cool F# Language" />  
    <add id="17" title="Nancy Framework" description="Lightweight, low ceremony ASP.Net MVC framework" />  

To my eye, this is easier to manage. There’s a clear indication of what the configuration is for (<BlogConfiguration>), there’s less, “tag soup” using XML attributes and I clearly can’t spell, “Technologies”.

It’s relatively straight forward to write one these. To begin with, define a class as follows:

using System.Configuration;  
public class BlogConfiguration : ConfigurationSection  
    [ConfigurationProperty("title", IsRequired = true)]  
    public string Title  
        get { return this["title"] as string; }  
    [ConfigurationProperty("postsPerPage", IsRequired = false, DefaultValue = 3)]  
    public int PostsPerPage  
        get { return (int)this["postsPerPage"]; }  
    [ConfigurationProperty("categories", IsRequired = false)]  
    public BlogCategoryConfigurationCollection Categories  
        get { return this["categories"] as BlogCategoryConfigurationCollection; }  

I’ve removed most of the properties for clarity. There’s a gist of this class available.

The [ConfigurationProperty] attribute defines the name of configuration attribute. You can also specify additional attributes including whether the property is required and its default value.

The Categories configuration requires two classes. One to define a “Category Element” and another to define the collection.

public class BlogCategoryConfigurationElement : ConfigurationElement  
    [ConfigurationProperty("id", IsRequired = true)]  
    public string Id  
        get { return this["id"] as string; }  
    [ConfigurationProperty("title", IsRequired = true)]  
    public string Title  
        get { return this["title"] as string; }  
    [ConfigurationProperty("description", IsRequired = true)]  
    public string Description  
        get { return this["description"] as string; }  
public class BlogCategoryConfigurationCollection : ConfigurationElementCollection  
    public BlogCategoryConfigurationElement this[int index]  
        get { return BaseGet(index) as BlogCategoryConfigurationElement; }  
            if (BaseGet(index) != null)  
            BaseAdd(index, value);  
    protected override ConfigurationElement CreateNewElement()  
        return new BlogCategoryConfigurationElement();  
    protected override object GetElementKey(ConfigurationElement element)  
        return ((BlogCategoryConfigurationElement)element).Id;  

The ConfigurationElement is much like the ConfigurationSection. In this case it is used to define the structure of a category.

The ConfigurationElementCollection is more work. The required elements are an indexer, a factory method to create a new element and a method to retrieve the element’s key. Standard fare for collection overrides.

Finally, the Web.config has to be told about the new custom configuration section. This also wires-up IntelliSense support.

    <section name="BlogConfiguration" type="bloget2.Models.BlogConfiguration" />  

To reference the configuration in your code:

var blogConfiguration = (BlogConfiguration)ConfigurationManager.GetSection("BlogConfiguration");  
blog.Title = blogConfiguration.Title;  

Notice the use of properties instead of string-based indexers.

Related links:

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