Writing a Complex Custom Configuration Section

Here I posted another entry, showing the implementation of a simple configuration section. Now consider the following listing: 

<customSection>
  <elements>
     <add name="FirstAssembly.FirstType" assembly="FirstAssembly" shouldrun="true" />
     <add name="SecondAssembly.SecondType" assembly="SecondAssembly" shouldrun="true" />
  </elements>
</customSection>

Here, we have "n" number of elements in the custom configuration section. To handle this kind of scenario, System.Configuration namespace provides you with the ConfigurationPropertyCollection class and ConfigurationPropertyCollectionAttribute class. Your can use ConfigurationPropertyCollection to programmatically write your configuration section and ConfigurationPropertyCollectionAttribute can be used to do the same job declaratively.

Listed below are the steps involved in creating a custom configuration section handler with multiple entries.

1. Define a class (say CustomElement) to represent configuration section by inheriting it from ConfigurationElement class
2. Define a class to represent your configuration collection (say CustomElementCollection) by inheriting it from ConfigurationElementCollection. This will hold a collection of the type you defined in step 1
3. Define a class to represent your custom section (say CustomSection) by inheriting it from ConfigurationSection and implement a property of the type that you defined in step 2

Here is the listing for CustomElement class:

public class CustomElement : ConfigurationElement
{
    public CustomElement()
    {
    }

    [ConfigurationProperty("name", IsRequired = true)]
    public string Name
    {
        get { return (string)this["name"]; }
        set { this["name"] = value; }
    }

    [ConfigurationProperty("assembly", IsRequired = true)]
    public string Assembly
    {
        get { return (string)this["assembly"]; }
        set { this["assembly"] = value; }
    }

    [ConfigurationProperty("shouldrun", IsRequired = true)]
    public bool ShouldRun
    {
        get { return (bool)this["shouldrun"]; }
        set { this["shouldrun"] = value; }
    }
}

and here is the listing for CustomElementCollection class. Its implementation is similar to any other Collection class.

public class CustomeElementCollection : ConfigurationElementCollection
{
    public CustomeElementCollection()
    {
        CustomElement myElement = (CustomElement)CreateNewElement();
        Add(myElement);
    }

    public void Add(CustomElement customElement)
    {
        BaseAdd(customElement);
    }

    protected override void BaseAdd(ConfigurationElement element)
    {
        base.BaseAdd(element, false);
    }

    public override ConfigurationElementCollectionType CollectionType
    {
        get
        {
            return ConfigurationElementCollectionType.AddRemoveClearMap;
        }
    }

    protected override ConfigurationElement CreateNewElement()
    {
        return new CustomElement();
    }

    protected override object GetElementKey(ConfigurationElement element)
    {
        return ((CustomElement)element).Name;
    }

    public CustomElement this[int Index]
    {
        get
        {
            return (CustomElement)BaseGet(Index);
        }
        set
        {
            if (BaseGet(Index) != null)
            {
                BaseRemoveAt(Index);
            }
            BaseAdd(Index, value);
        }
    }

    new public CustomElement this[string Name]
    {
        get
        {
            return (CustomElement)BaseGet(Name);
        }
    }

    public int indexof(CustomElement element)
    {
        return BaseIndexOf(element);
    }

    public void Remove(CustomElement url)
    {
        if (BaseIndexOf(url) >= 0)
            BaseRemove(url.Name);
    }

    public void RemoveAt(int index)
    {
        BaseRemoveAt(index);
    }

    public void Remove(string name)
    {
        BaseRemove(name);
    }

    public void Clear()
    {
        BaseClear();
    }
}

and finally, here is the listing for CustomSection class:

class CustomSection : ConfigurationSection
{
    CustomElement element;
    public CustomSection()
    {
        element = new CustomElement();
    }

    [ConfigurationProperty("elements", IsDefaultCollection = false)]
    [ConfigurationCollection(typeof(CustomeElementCollection), AddItemName = "add",
        ClearItemsName = "clear",
        RemoveItemName = "remove")]
    public CustomeElementCollection Elements
    {
        get
        {
            return (CustomeElementCollection)base["elements"];
        }
    }
}

Next, add the following settings to your configuration file:

<configSections>
  <section name="customSection" 
  type="ConfigurationDemo.CustomSection, ConfigurationDemo" />
</configSections>

<customSection>
  <elements>
    <add name="FirstAssembly.FirstType" 
    assembly="FirstAssembly" shouldrun="true" />
    <add name="SecondAssembly.SecondType" 
    assembly="SecondAssembly" shouldrun="true" />
  </elements>
</customSection>

In the end, put this custom section to use like this:

CustomSection myCustomSection = (CustomSection)ConfigurationManager.GetSection("customSection");

foreach (CustomElement element in myCustomSection.Elements)
{
    if (element.Name != null && element.Name != "")
    {
        string name = element.Name;
        string assembly = element.Assembly;
        bool shouldrun = element.ShouldRun;
    }
}