How would I write this VB.Net loop functionally?

Question

I have a VB.Net function that translates a NameValueColletion to an IDictionary . How would I write this functionally (with Select , etc. instead of a loop)?

<Extension()>
Public Function ToDictionary(ByVal source As NameValueCollection)
        As IDictionary(Of String, String)
    Dim ret = New Dictionary(Of String, String)
    Dim keys = source.Keys
    For Each key In keys
        Dim sKey = TryCast(key, String)
        Dim sVal = TryCast(source(key), String)
        If sKey Is Nothing OrElse sVal Is Nothing Then Continue For
        ret(sKey) = sVal
    Next
    Return ret
End Function

Answer 1

Return source.Cast(Of String)().
             ToDictionary(Function(key) key, Function(key) source(key))