null value problem with storeprocedure using linq

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.NET3.5

ASP

hi ,

i have created a store procedure and used taht store procedure to insert data to table.But it create problem when the int or datetime text value is null.How do i handle it?

the code is in below

 DATAClassesDataContext db = new DATAClassesDataContext();

 int result = db.insertagent(txtagent.Text, txtfather.Text, Convert.ToDateTime(txtdob.Text), txtaddress.Value, Convert.ToInt32(txtpin.Text),
  Convert.ToInt32(txtage.Text), txtphoneno.Text, txtbankname.Text,
Convert.ToInt32(txtaccountno.Text), txtbankaddress.Value, txtpancardno.Text, txtnominee.Text, rbtrelationship.Text, Convert.ToInt32(txtNomineeage.Text), txtIntroducernamet.Text, Convert.ToInt32(txtIntroducercode.Text),
                                       txtrank.Text, Convert.ToInt32(txtissuerank.Text), Convert.ToInt32(txtcustomerid .Text), txtpalnbname.Text,
                                      Convert.ToInt32(txtplanbcode.Text), txtteama.Text, txtteamb.Text, txtepinno.Text, txtserialno.Text, Convert.ToDateTime(txtfromdate.Text),
                                       txtemail.Text);

Thanks in Advance!!!!!!!!!!