Configuration element containing a collection of child elements

Question

I want to have a custom section in my web.config like so:

<MyMainSection attributeForMainSection = "value foo">

    <add name = "foo" 
    type = "The.System.Type.Of.Foo, Assembly, Qualified Name Type Name" />

    <add name = "bar" 
    type = "The.System.Type.Of.Bar, Assembly, Qualified Name Type Name" />

</MyMainSection>

I have defined the following code:

using System.Configuration;

class MyMainSection : ConfigurationSection
{
    /*I've provided custom implemenation. 
      Not including it here for the sake of brevity. */ 
    [ConfigurationProperty("attributeForMainSection")]
    public string AttributeForMyMainSection { get; set; }

    [ConfigurationProperty("add")]
    public AddElement TheAddElement { get; set; }

    private class AddElement: ConfigurationElement
    {
        /* Implementation done */
    }

}

Should this property TheAddElement be IEnumerable<AddElement> or just AddElement if I want to allow multiple add elements?

Answer 1

Neither, you would introduce a new ConfigurationCollectionElement instead e.g.

Section

class MyMainSection : ConfigurationSection
{
    [ConfigurationProperty("", IsRequired=true, IsDefaultCollection=true)]
    public AddElementCollection Instances 
    {
        get { return (AddElementCollection) this[""]; }
        set { this[""] = value; }
    }
}

Collection

public class AddElementCollection : ConfigurationElementCollection 
{
    protected override ConfigurationElement CreateNewElement() 
    {
        return new AddElement();
    }

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

Element

private class AddElement: ConfigurationElement
{
    [ConfigurationProperty("name", IsKey=true, IsRequired=true)]
    public string Name 
    {
        get { return (string) base["name"]; }
        set { base["name"] = value; 
    }
    ...
}