public ICEPExpression <IDictionary <IndexType, DataType> > GroupBy <DataType, IndexType>(Func <DataType, IndexType> groupFunc) { IndexBlock <IndexType, DataType> block = blockFactory.CreateIndexBlock(groupFunc, true, name + "Group"); return(CreateChildExpr <IDictionary <IndexType, DataType> >(this, block, name + "GroupBy.")); }