VB.net WPF :Unable to cast object of type 'Ocean.GeneralMast

Question

Dear Experts,

I'm using wpf with vb.net. When i tried below code then i'm getting an error 

Error--------------
Unable to cast object of type 'Ocean.GeneralMaster' to type 'System.Windows.Forms.Form'.
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 Dim objForm As Form

        Dim sValue As String

        Dim FullTypeName As String

        Dim FormInstanceType As Type

        ' Form class name

        sValue = "GeneralMaster"

        ' Assume that form classes' namespace is the same as ProductName

        FullTypeName = "Ocean" & "." & sValue

        ' Now, get the actual type

        FormInstanceType = Type.GetType(FullTypeName, True, True)

        ' Create an instance of this form type

        objForm = CType(Activator.CreateInstance(FormInstanceType), Form)

        ' Show the form instance

        objForm.Show()