using System;

public class Program

{

    public static void Main()

    {

        // METODO 1

        var valoreLettoDalDataRow = 5;

        var exampleViewModel = new ExampleViewModel();

        if (!Convert.IsDBNull(valoreLettoDalDataRow))

        {

            exampleViewModel.Number = Convert.ToInt32(valoreLettoDalDataRow);

        }

        Console.WriteLine(exampleViewModel.Number.HasValue ? exampleViewModel.Number.Value.ToString() : "null");

        // METODO 2

        /*var valoreLettoDalDataRow = DBNull.Value;

        var exampleViewModel = new ExampleViewModel

        {

            Number = Convert.IsDBNull(valoreLettoDalDataRow) ? null : (int?)Convert.ToInt32(valoreLettoDalDataRow) // Occorre castare a int?

        };

        Console.WriteLine(exampleViewModel.Number.HasValue ? exampleViewModel.Number.Value.ToString() : "null");*/

    }

    private class ExampleViewModel

    {

        public int? Number { get; set; }

    }

}