VB.net SQL make sure only single value returned

Hi. I am using the following code to pull a single result from a SQL table.
I need a way to check if the result returns more than one value first.
Is there a way to build that into this code? If not what code would I need
to run first to see if there is a single value returned for this SQL statement

                Dim connection As New SqlConnection(oConnectionString)
                Dim cmd As New SqlCommand(sSQL, connection)
                connection.Open()
                oResult = cmd.ExecuteScalar.ToString
                If IsDBNull(oResult) = True Then
                    Get_Value = "Null"
                Else
                    Get_Value = oResult
                End If
                connection.Close()