Union Lists using IEqualityComparer
<p>I'we got two Lists of my class Nomen: </p>

<pre><code>var N1 = new List&lt;Nomen&gt;(); 
var N2 = new List&lt;Nomen&gt;(); 


public class Nomen
{
    public string Id;

    public string NomenCode;

    ...

    public string ProducerName;

    public decimal? minPrice;
}
</code></pre>

<p>I need to join them. I used to do it like this:</p>

<pre><code>result = N2.Union(N1, new NomenComparer()).ToList();

class NomenComparer : IEqualityComparer&lt;Nomen&gt;
{
    public bool Equals(Nomen x, Nomen y)
    {
        return x.Equals(y);
    }

    public int GetHashCode(Nomen nomen)
    {
        return nomen.GetHashCode();
    }
}

    public override int GetHashCode()
    {
        return (Id + NomenCode + ProducerName).GetHashCode();
    }

    public bool Equals(Nomen n)
    {
        if (!String.IsNullOrEmpty(Id) &amp;&amp; Id == n.Id) return true;

        return (NomenCode == n.NomenCode &amp;&amp; ProducerName == n.ProducerName);
    }
</code></pre>

<p>As you can see, if Ids or NomenCode and ProducerName are equal, for me it's the same Nomen. 
now my task have changed and I need to take, if they equal, the one with less minPrice. Please, help me to solve this problem. 
Tried to do the same with linq, but failed</p>

<pre><code>        var groups = (from n1 in N1
                      join n2 in N2
                      on new { n1.Id, n1.NomenCode, n1.ProducerName } equals new { n2.Id, n2.NomenCode, n2.ProducerName }
                      group new { n1, n2 } by new { n1.Id, n1.NomenCode, n1.ProducerName } into q
                      select new Nomen()
                      {
                          NomenCode = q.Key.NomenCode,
                          ProducerName = q.Key.ProducerName,
                          minPrice = q.Min(item =&gt; item.minPrice)
                      }).ToList();
</code></pre>

<p>Mostly because I need to join Lists by Ids OR {NomenCode, ProducerName} and I don't know how to do it.</p>