vb.net - Convert DBNull To String Before Populating Data To Datagridview -

i need way convert dbnull string when populating data database datagridview. below code

 private sub fetchdata()      sql = "select contributiontype,status,paymethod,bankname,accountno,amount,fullname,district,refno,contributorgrp"     sql &= " tblincome txnid=@id"      command = new oledbcommand(sql, connection)     command.parameters.add(new oledbparameter("@id", oledbtype.varchar)).value = lbltxnid.text      adapter = new oledbdataadapter(command)     dt = new datatable     adapter.fill(dt)        each row in dt.rows         populategrid(row(0), row(1), row(2), row(3), row(4), row(5), row(6), row(7), row(8), row(9))     next      dt.rows.clear()     dt.dispose() end sub  private sub populategrid(contributiontype string, status string, paymethod string, bankname string _                          , accountno string, amount double, fullname string, district string _                          , refno string, contributorgrp string)      dim row string() = new string() {contributiontype, status, paymethod, bankname, accountno, amount.tostring("n") _                                        , fullname, district, refno, contributorgrp}     dgvcontributions.rows.add(row) end sub 

the fields bankname , accountno allow null entries ones null values.

you use method:

public shared function convertdbval(of t)(obj object, optional nullfallbackval t = nothing) t     if obj nothing orelse obj.equals(dbnull.value)         return nullfallbackval     else         return ctype(obj, t)     end if end function 

usage:

dim bankname string = convertdbval(row(3), "") dim accnumber = convertdbval(row(4), "") 

if don't specify (optional) fallback-value have specify type explicitly:

dim bankname string = convertdbval(of string)(row(3)) 

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