title: Setting CustomSqlType on References
body: <p>I have a situation where my primary key is a char(2) in SqlServer 2008, and I want to reference it in a one-to-many relationship, but the ManyToOneBuilder (which is returned by ClassMap&lt;>.References()) doesn't have a CustomSqlType() method. Specifically:</p>
  
  <pre><code>public class State
  {
      // state FIPS code is 2 characters
      public virtual string StateCode { get; set; }
      public virtual ICollection&lt;County&gt; { get; set; }
  }
  
  public class County
  {
      // state-county FIPS code is 5 characters
      public virtual string StateCountyCode { get; set; }
      public virtual State State { get; set; }
  }
  public class StateMap : ClassMap&lt;State&gt;
  {
      public StateMap()
      {
          Id(e =&gt; e.StateCode).CustomSqlType("char(2)").GeneratedBy.Assigned();
      }
  }
  
  public class CountyMap : ClassMap&lt;County&gt;
  {
      public CountyMap()
      {
          Id(e =&gt; e.StateCountyCode).CustomSqlType("char(5)").GeneratedBy.Assigned();
          References(e =&gt; e.State, "StateCode")
          // Here's what I want to do, but can't because the method is not 
          // implemented on the class ManyToOneBuilder:
              .CustomSqlType("char(2)");
      }
  }
  </code></pre>
  
  <p>Is there any way to accomplish this without modifying the ManyToOneBuilder? Is there a way to automatically map the FK (i.e. County.StateCode) to the correct type? It's trivial to add CustomSqlType to ManyToOneBuilder, but is that the right thing to do?</p>