This code: var s1 = session.Query.All<myentity>().Select(a => new { T1 = a.Text, T2 = a.Text }); var s2 = session.Query.All<myentity>().Select(a => new { T1 = a.Text, T2 = a.Text });

var s3 = s1.Concat(s2);
var sss = s3.ToArray();

Raises exception: System.ArgumentException occurred

  Message=An item with the same key has already been added.
  Source=mscorlib
  StackTrace:
       at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
       at Xtensive.Storage.Rse.ColumnCollection.Initialize() in c:\Projects\dataobjects.net\Xtensive.Orm\Xtensive.Orm\Storage\Rse\ColumnCollection.cs:line 43
  InnerException: