data continuously inserted in table

i try send data in table when time exceed on 5 mint data inserted data insert multiple times want submit data 1 time 
i.e. 1 row insert 1 number

try

if (timediff.totalminutes > 5)
{
dataclasses1datacontext db = new dataclasses1datacontext();
var u = db.tbl_urgent_contacts;
foreach (var in u)
{
tbl_outbox tb = new tbl_outbox();
tb.fromsim_no = a.simno;
tb.tosim_no = a.simno; 
tb.totext = "check abc";
tb.reply = "na";
tb.response = "na";
tb.regno = "na";
tb.datetd = datetime.now;
tb.ffid = "na";
tb.userid = "you";
tb.fromtext = "check abc";
db.tbl_outboxes.insertonsubmit(tb);
db.submitchanges();
} 
}

maybe exclude existing entries this:

   var u = db.tbl_urgent_contacts.where( … );

the “…” condition depends on details of tables , include ‘!db.tbl_outboxes.contains(…)’ expression, etc.

another solution remove processed entries tbl_urgent_contacts if no more needed, or add additional column (bit, boolean), called processed example. have:

  var u = db.tbl_urgent_contacts.where( c => ! c.processed );
  foreach (var in u)
  {
    a.processed = true;
    . . .
  }

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