I am setting up some fields in the mapper to Use Nullable Generic. This setting works ok if the field is a numeric type, but if the field is varchar, the code the mapper generates is causing the build to fail. Here is the code for the field:

''' <summary>
''' Test
''' </summary>
''' <remarks></remarks>
<Browsable(False), _
BusinessFieldDisplayInEditor(), _
Description("Test"), _
DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)> _
Public Property [Test]() As Nullable(Of System.String)
  Get
    Dim loValue As Object
    loValue = Me.CurrentRow.Item("Test")
    If loValue Is DBNull.Value Then
        Return CType(Nothing, Nullable(Of System.String))
    Else
        Return CType(loValue, Nullable(Of System.String))
    End If
  End Get
  Set(ByVal value As Nullable(Of System.String))
    If value.HasValue Then
      Me.CurrentRow.Item("Test") = value.Value
    Else
      Me.CurrentRow.Item("Test") = DBNull.Value
    End If
  End Set
End Property

The hilighted code is giving the error:

Error 1 Type argument 'String' does not satisfy the 'Structure' constraint for type parameter 'T' ...

Anyone know why this is? Thanks!