title: System.MissingMethodException after upgrading from EF 6.0 Beta to RC
body: <p>what does this mean?</p>
  
  <blockquote>
    <p>System.MissingMethodException was unhandled by user code<br>
    HResult=-2146233069   Message=Method not found:
    'System.Data.Entity.ModelConfiguration.Configuration.PrimitivePropertyConfiguration
    System.Data.Entity.ModelConfiguration.Configuration.StructuralTypeConfiguration<code>1.Property(System.Linq.Expressions.Expression</code>12&lt;!0,!!0&gt;&gt;)'.
    Source=Att.Uds.DataLayerMappings   StackTrace:
           at Att.Uds.DataLayerMappings.ItemTypeItemConfiguration..ctor()
           at Att.Uds.DataLayerMappings.UdsContext.OnModelCreating(DbModelBuilder
    modelBuilder) in
    c:\TFS\ATS-MSDev\UDS\Dev\Code\Att.Uds.DataLayerMappings\UdsContext.cs:line
    163
           at System.Data.Entity.DbContext.CallOnModelCreating(DbModelBuilder
    modelBuilder)
           at System.Data.Entity.Internal.LazyInternalContext.CreateModelBuilder()
           at System.Data.Entity.Internal.LazyInternalContext.CreateModel(LazyInternalContext
    internalContext)
           at System.Data.Entity.Internal.RetryLazy2.GetValue(TInput input)   InnerException:</p>
  </blockquote>
  
  <p>Error happens on this class:</p>
  
  <pre><code>namespace Contoso.Fabrikam.DataLayerMappings
  { 
    public abstract class NamedEntityConfiguration&lt;TEntity&gt; : EntityBaseConfiguration&lt;TEntity&gt; where TEntity : NamedEntity
    {
      public ConfigurationColumn NameColumn;
      protected new int LastOrdinalPosition
      {
        get
        {
          return (NameColumn.Ordinal);
        }
      }
      public NamedEntityConfiguration() &lt;=== EXCEPTION HERE
      {
        NameColumn = new ConfigurationColumn() { Ordinal = base.LastOrdinalPosition+1, Name = "Name", IsRequired = true, Length = 128 };
        this.Property(t =&gt; t.Name)
          .HasColumnName(NameColumn.Name)
          .HasColumnOrder(NameColumn.Ordinal)
          .HasMaxLength(NameColumn.Length);
        if(NameColumn.IsRequired)
        {
          this.Property(t =&gt; t.Name).IsRequired();
        }
      }
    }
  }
  </code></pre>
  
  <p>Thank you</p>