get list from based on another list
<p>I asked this question earlier, but I over simplified it, and I still don't know how to do it in a better way than I'm doing (for).</p>

<p>I got two lists.</p>

<p>One, a list of facebook friends, a simple object, consider facebook.id the only property.</p>

<p>Second, a list of users, it's a more complex object, because each user gets a lists of providers inside (facebook, twitter, etc), but the providers list can be null, and if not null, not necessarily the provider is a facebook one. So:</p>

<pre><code>public class EFacebook
{
    public long Id { get; set; }
}

public class EUser
{
    public long Id { get; set; }
    /// &lt;summary&gt;
    /// Nullable
    /// &lt;/summary&gt;
    public List&lt;EProvider&gt; EProviders { get; set; }
}

public class EProvider
{
    public enum EnumProviderType
    {
        Facebook = 2,
        Twitter = 3
    }
    public EnumProviderType ProviderType { get; set; }
    public string Id { get; set; }
}
</code></pre>

<p>What I need is to filter the facebook list to get all the facebook friends that are users and get all the facebook friends that are not users.</p>
