How to define a Property in VB.NET using the generic SortedList (Of T, V)?

Can an expert tell me how to use the generic SortedList as a Property?  Whenever I try the code below, I get an error.

500 points to the expert who can answer the question!

Public Property Variables() As SortedList(Of String, Variable)()
      Get
        Return (_slVariables)
      End Get
      Set(ByVal svalue As SortedList(Of String, Variable()))
        _slVariables = svalue
      End Set
    End Property

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