Here is an example
OleDbConnection con = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Path.GetDirectoryName(Application.ExecutablePath) + "\\NBS.mdb;");
OleDbCommand cmd;
string strSQL1 = ("insert into DailyTrans_Master (ReceiptNo,ReceiptDate,Cust_ID,Amt_paid,ForMonth,ForYear)");
strSQL1 += ("values ('" + txtReceiptNo.Text + "',Date()," + txtCustomerID.Text + "," + txtAmt.Text + ",'" + cmbMonth.Text + "','" + cmbYear.Text + "')");
con.Open();
cmd = new OleDbCommand(strSQL1, con);
cmd.ExecuteNonQuery();
con.Close();
string strSQL = "update Receipt_Master_" + cmbYear.Text + " set [Jan]= " + txtAmt.Text + " where [Cust_ID]= " + txtCustomerID.Text + "";
con.Open();
cmd = new OleDbCommand(strSQL, con);
cmd.ExecuteNonQuery();
con.Close();
string SQL = "delete from area_master where area_Name = '" + txtAreaName.Text + "' and area_Code = '" + txtAreaCode.Text + "'";
con.Open();
cmd = new OleDbCommand(SQL, con);
cmd.ExecuteNonQuery();
con.Close();