vb.net - NullReferenceException error in VB Application? -

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i'm building voting system calls, , have tried build in vb. far have:

    dim con new oledb.oledbconnection     dim dbprovider string     dim dbsource string      dbprovider = "provider=microsoft.jet.oledb.4.0;"     dbsource = "data source = c:\phonepoll.mdb"      con.connectionstring = dbprovider & dbsource      con.connectionstring = "provider=microsoft.jet.oledb.4.0;data source = c:\phonepoll.mdb"      con.open()      'sql = "select * voting"     'da = new oledb.oledbdataadapter(sql, con)     'da.fill(ds, "voting")      if inc <> -1          dim cb new oledb.oledbcommandbuilder(da)         dim dsnewrow datarow          dsnewrow = ds.tables("voting").newrow()         dsnewrow.item("voted") = radiobutton1.checked.tostring         dsnewrow.item("voted") = radiobutton2.checked.tostring         dsnewrow.item("voted") = radiobutton3.checked.tostring         dsnewrow.item("voted") = radiobutton4.checked.tostring          ds.tables("voting").rows.add(dsnewrow)          da.update(ds, "voting")          msgbox("new record added database")      end if      msgbox("phone call has been logged")      con.close()

this code contained within "record call" button. on form, there 4 radio buttons, different text values should entered in "voting" table.

my problem when select radio button , click on "record button" displays error:

nullreferenceexception: object reference not set instance of object.

this error displayed on line

dsnewrow = ds.tables("voting").newrow()

i'm not sure i've done wrong.

cheers help!

i assuming in real code don't have sql , fill() method dataset commented out , typo in code above - right? if wrong , block of code commented out, dataset null , that's issue...


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