I'm working on a project where we define some interfaces (possibly in a hierarchy) and the actual entities are generated runtime. Basically we don't know any entity at compile time and always work with the interfaces in queries etc.

Basically we have a structure similar to this:

Record / IRecord (represents our "root entity". All dynamic entities will implement this and it defines the HierarchyRoot) IPerson IEmployee : IPerson

In a generic grid method we use for grid binding we have this method:

var records = session.Query.All(RecordType).Cast<irecord>();

RecordType could be either IRecord, IPerson or IEmployee. Since our method returns a IQueryable<irecord>, we need to do the .Cast<irecord> for the signature to match. It works well when we do this with "real entities", but when RecordType = IPerson/IEmployee, the cast method results in this exception:

[KeyNotFoundException: The given key was not present in the dictionary.] System.Collections.Generic.Dictionary2.get_Item(TKey key) +9627953 Xtensive.Orm.Linq.Translator.VisitCast(Expression source, Type targetType, Type sourceType) +591 Xtensive.Orm.Linq.Translator.VisitQueryableMethod(MethodCallExpression mc, QueryableMethodKind methodKind) +239 Xtensive.Linq.QueryableVisitor.VisitMethodCall(MethodCallExpression mc) +294 Xtensive.Orm.Linq.Translator.VisitMethodCall(MethodCallExpression mc) +3368 Xtensive.Linq.ExpressionVisitor1.Visit(Expression e) +428 Xtensive.Orm.Linq.Translator.Visit(Expression e) +170 Xtensive.Orm.Linq.Translator.VisitSequence(Expression sequenceExpression, Expression expressionPart) +743 Xtensive.Orm.Linq.Translator.VisitWhere(Expression expression, LambdaExpression le) +64 Xtensive.Orm.Linq.Translator.VisitQueryableMethod(MethodCallExpression mc, QueryableMethodKind methodKind) +5393 Xtensive.Linq.QueryableVisitor.VisitMethodCall(MethodCallExpression mc) +294 Xtensive.Orm.Linq.Translator.VisitMethodCall(MethodCallExpression mc) +3368 Xtensive.Linq.ExpressionVisitor1.Visit(Expression e) +428 Xtensive.Orm.Linq.Translator.Visit(Expression e) +170 Xtensive.Orm.Linq.Translator.VisitSequence(Expression sequenceExpression, Expression expressionPart) +743 Xtensive.Orm.Linq.Translator.VisitAggregate(Expression source, MethodInfo method, LambdaExpression argument, Boolean isRoot, MethodCallExpression expressionPart) +367 Xtensive.Orm.Linq.Translator.VisitQueryableMethod(MethodCallExpression mc, QueryableMethodKind methodKind) +4574 Xtensive.Linq.QueryableVisitor.VisitMethodCall(MethodCallExpression mc) +294 Xtensive.Orm.Linq.Translator.VisitMethodCall(MethodCallExpression mc) +3368 Xtensive.Linq.ExpressionVisitor1.Visit(Expression e) +428 Xtensive.Orm.Linq.Translator.Visit(Expression e) +170 Xtensive.Orm.Linq.Translator.Translate() +22 Xtensive.Orm.Linq.QueryProvider.Translate(Expression expression) +71