I noticed the following code:

_E As Generic.Dictionary(Of String, String) = New
Generic.Dictionary(Of String, String)

' assume _E has 1000s of keys

   Dim UA As String = "v"
   Dim SE As String
   Dim SEObj As Object
   Dim res As Boolean

           SEObj = _E(UA) ' value can't be Nothing
           If (SEObj IsNot Nothing) Then
               SE = SEObj
           End If

..is about 3x faster than..

           res = _E.ContainsKey(UA)
           If res Then
               SE = _E(UA)
           End If

Why is ContainsKey so much slower than a direct lookup?