How to read only the error line number from exception

In asp.net i am trying to read only error message after i caught exception,
how can I do it

I would realy appreciate any examples

Thanks

Try 
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  Catch ex As Exception
 
                'ADDING THE MORE MEANINGFUL INFORMATION TO EXCEPTION
                'BUT ONLY ADD NEW EXCEPTION THEIR IS NOT ALREADY ANY DETAIL ADDED BEFORE
                If ex.Data("Class") Is Nothing Then
                    ex.Data.Clear()
                    ex.Data("Class") = System.Reflection.MethodBase.GetCurrentMethod().DeclaringType.ToString()
                    ex.Data("Function") = System.Reflection.MethodBase.GetCurrentMethod().Name
                End If
 
                'THROWING THE EXCEPTION AGAIN SO IT WILL BE CATCH AT THE HIGHER LEVEL
                Throw ex
 
            End Try

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