Recently I was asked how can you get a list of anonymous type member names given a query of anonymous types. The quick answer is that you can use a quick bit of reflection to get back the names.
Public Function GetAnonymousTypeMemberNames(Of T)(ByVal anonymousType As T) As List(Of String) Dim type = GetType(T) Dim list = New List(Of String) For Each cur In type.GetProperties(Reflection.BindingFlags.Public Or Reflection.BindingFlags.Instance) list.Add(cur.Name) Next Return list End Function
The longer question is how can you get back a list of anonymous type member names given a query result? As long as you know the query will be populated you can just use the first member to get your result.
Dim q = From it In "astring" Select a = it, b = it & "b" GetAnonymousTypeMemberNames(q.First())
However you can’t guarantee that a query will always have data in it. Another route is to consider the contract of the From … Select statement. This will produce a query which implements IEnumerable(Of T). For a query T will be the anonymous type that is generated. We can query the metadata of the returned type to get the System.Type for the anonymous type regardless of the type actually implementing IEnumerable(Of T).
Dim q = From it In "astring" Select a = it, b = it & "b" Dim enumerableInterface = GetType(IEnumerable(Of )) Dim enumerableType = q.GetType().GetInterface(enumerableInterface.FullName) Dim anonymousTypeType = enumerableType.GetGenericArguments(0)
 This is assuming that you didn’t write a query which returns a field directly and avoids creating the anonymous type.