title: Invalid index 1 for this SqlParameterCollection with Count=1
body: <p>What I have noticed is that the in Ncv the Report field that i am referencing is not generated. Below is the error I am receiving.</p>
  
  <p>Here is what my domain looks like and the error i receive is Invalid index 1 for this SqlParameterCollection with Count=1.</p>
  
  <pre><code>public class NcvMap : SubclassMap&lt;Ncv&gt;
  {
      public NcvMap()
      {
          HasManyToMany&lt;Document&gt;(x =&gt; x.Technician)
              .Cascade.All();
  
          HasManyToMany&lt;Document&gt;(x =&gt; x.Neurologist)
              .Cascade.All();
  
          HasManyToMany&lt;Document&gt;(x =&gt; x.Transcriber)
              .Cascade.All();
  
          References&lt;Document&gt;(x =&gt; x.Report).Nullable();
      }
  }
  
  public class Ncv : Report
  {
      public virtual IList&lt;Document&gt; Technician { get; private set; }
      public virtual IList&lt;Document&gt; Neurologist { get; private set; }
      public virtual IList&lt;Document&gt; Transcriber { get; private set; }
      public virtual Document Report { get; set; }
      public virtual NcvType Type { get; set; }
  
      public Ncv()
      {
          this.Technician = new List&lt;Document&gt;();
          this.Neurologist = new List&lt;Document&gt;();
          this.Transcriber = new List&lt;Document&gt;();
      }
  }
  
  public class Report : BaseModel
  {
      public virtual Patient Patient { get; set; }
      public virtual ReportStatus Status { get; set; }
      public virtual DateTime Appointment { get; set; }
      public virtual long Kareo_id { get; set; }
      public virtual IList&lt;ReportLog&gt; Logs { get; private set; }
  
      public Report() 
      {
          this.Status = ReportStatus.New;
          this.Logs = new List&lt;ReportLog&gt;();
      }
  
      public virtual void AddLog(ReportLog log)
      {
          log.Report = this;
          this.Logs.Add(log);
      }
  }
  
  public class ReportMap : ClassMap&lt;Report&gt;
  {
      public ReportMap()
      {
          Id(x =&gt; x.Id);
          Map(x =&gt; x.CreateDate);
          Map(x =&gt; x.LastModified);
          Map(x =&gt; x.Appointment);
          Map(x =&gt; x.Status).CustomType&lt;int&gt;();
          Map(x =&gt; x.Kareo_id);
  
          HasMany&lt;ReportLog&gt;(x =&gt; x.Logs)
              .Cascade.All();
  
          References&lt;Patient&gt;(x =&gt; x.Patient);
      }
  }
  </code></pre>