vb.net - why 0, not Nothing in VB System.Data.DataTable -

the codes:

        private m_log_datatable system.data.datatable = nothing         private m_freq string = nothing         private m_r single = nothing         private m_l single = nothing         private m_c single = nothing         private m_rp single = nothing         private m_rs single = nothing         private m_z single = nothing         private m_esr single = nothing         private m_dcr single = nothing         private m_q single = nothing         private m_d single = nothing 

...

    private sub log()         try             m_freq = nothing             m_r = nothing             m_l = nothing             m_c = nothing             m_rp = nothing             m_rs = nothing             m_z = nothing             m_esr = nothing             m_dcr = nothing             m_q = nothing             m_d = nothing             m_value = nothing             m_unit = nothing             m_log_datatable.rows.add(datetime.now, getdut(), getmode(), m_freq, m_r, m_l, m_c, m_r, m_rs, m_z, m_esr, m_dcr, m_q, m_d)'line1             m_log_datatable.rows.add(datetime.now, getdut(), getmode(), nothing, nothing, nothing, nothing, nothing, nothing, nothing, nothing, nothing, nothing, nothing)'line2         catch ex exception             msgbox("exception when logging:" + ex.message)         end try     end sub 

output:

why line1 (in above codes) write 0 datatable instead of nothing? should do?

thanks

you need use nullable type. change of single types single? , try again.

private m_r single? = nothing private m_l single? = nothing  // etc 

as gabor commented, you'll need access value property or 1 of other methods available nullable(of t).

m_r.value                 ' access underlying value  m_r.getvalueordefault()   ' underlying value or, if none, default underlying type  m_r.getvalueordefault(3)  ' underlying value or, if none, default value decide