ConfigurationElementCollection and Linq

Question

I've written some custom configuration collections, elements etc. Now, I'd like to do a simple Linq statement:

ServerDetails servers = ConfigurationManager.GetSection("serverDetails") as ServerDetails;
var server = from s in servers
             where s.Name == serverName
             select s;

I get the error:

Could not find an implementation of the query pattern for source type 'MyNamespace.ServerDetails'. 'Where' not found.

The ServerElement has two properties:

public class ServerElement : ConfigurationElement
{
    [ConfigurationProperty("ip")]
    public string IP
    {
        get { return (string)base["ip"]; }
        set { base["ip"] = value; }
    }

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

ServerDetails

public sealed class ServerDetails : ConfigurationSection
{
    [ConfigurationProperty("ServerCollection")]
    [ConfigurationCollection(typeof(ServerCollection), AddItemName = "add")]
    public ServerCollection ServerCollection
    {
        get { return this["ServerCollection"] as ServerCollection; }
    }
}

ServerCollection

public sealed class ServerCollection : ConfigurationElementCollection
{
    public void Add(ServerElement ServerElement)
    {
        this.BaseAdd(ServerElement);
    }

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

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

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

Am I missing something? Do I need to add something in so that I can use Linq with a custom configuration element?

By the way, I have using System.Linq; defined as I'm using it else where within the same class.

Answer 1

Okay, given that it's all weakly typed, you'll need to either call Cast<> or OfType<> explicitly, or give an explicit type to the range variable. You'll also need to specify the ServerCollection property on your ServerDetails. For example:

ServerDetails servers = (ServerDetails) ConfigurationManager.GetSection("serverDetails");
var server = from ServerElement s in servers.ServerCollection
             where s.Name == serverName
             select s;