Form Update Problem

I'm very new to asp.net and c#, I have been thrown in the deep end with a project at work and I'm really struggling to overcome this problem so any help will be very greatly appreciated.  I have a form with a number of textboxes that users use to update records in a database table with the use of a stored procedure.  The problem is that I can't get the form to just update the boxes that a user has filled out.  The form is working at the moment only if the user fills out all the boxes on the form which obviously is a waste of time if they only want to update one field.  I have tested the stored procedure and it works fine.  Please find the below code I'm trying to use!

 1 protected void Targets_Insert(object sender, EventArgs e)
2 {
3 System.Data.SqlClient.SqlConnection objConn = new System.Data.SqlClient.SqlConnection();
4 objConn.ConnectionString = "Data Source=SQL1;Password=rdbx;User ID=rdbx;Initial Catalog=Pronet";
5 objConn.Open();
6 System.Data.SqlClient.SqlCommand objCmd = new System.Data.SqlClient.SqlCommand("Update_Targets", objConn);
7 objCmd.CommandType = System.Data.CommandType.StoredProcedure;
8
9 System.Data.SqlClient.SqlParameter pdate = objCmd.Parameters.Add("@date", System.Data.SqlDbType.DateTime);
10 System.Data.SqlClient.SqlParameter pcontacts_new = objCmd.Parameters.Add("@contacts_new", System.Data.SqlDbType.Int);
11 System.Data.SqlClient.SqlParameter papplicants_new = objCmd.Parameters.Add("@applicants_new", System.Data.SqlDbType.Int);
12 System.Data.SqlClient.SqlParameter pclients_new = objCmd.Parameters.Add("@clients_new", System.Data.SqlDbType.Int);
13 System.Data.SqlClient.SqlParameter pHeadhunts_new = objCmd.Parameters.Add("@headhunts_new", System.Data.SqlDbType.Int);
14 System.Data.SqlClient.SqlParameter pCanvass_Calls_new = objCmd.Parameters.Add("@canvass_Calls_new", System.Data.SqlDbType.Int);
15 System.Data.SqlClient.SqlParameter pRegens_new = objCmd.Parameters.Add("@regens_new", System.Data.SqlDbType.Int);
16 System.Data.SqlClient.SqlParameter pJobs_Added_new = objCmd.Parameters.Add("@jobs_added_new", System.Data.SqlDbType.Int);
17 System.Data.SqlClient.SqlParameter pCVS_sent_new = objCmd.Parameters.Add("@CVS_sent_new", System.Data.SqlDbType.Int);
18 System.Data.SqlClient.SqlParameter puserid = objCmd.Parameters.Add("@userid", System.Data.SqlDbType.Int);
19 System.Data.SqlClient.SqlParameter punique_applicants_sent_new= objCmd.Parameters.Add("@unique_applicants_sent_new", System.Data.SqlDbType.Int);
20 System.Data.SqlClient.SqlParameter paverage_rate_new = objCmd.Parameters.Add("@average_rate_new", System.Data.SqlDbType.Int);
21 System.Data.SqlClient.SqlParameter paverage_salary_new = objCmd.Parameters.Add("@average_salary_new", System.Data.SqlDbType.Int);
22 System.Data.SqlClient.SqlParameter paverage_fee_new = objCmd.Parameters.Add("@average_fee_new", System.Data.SqlDbType.Int);
23 System.Data.SqlClient.SqlParameter pdeals_new = objCmd.Parameters.Add("@deals_new", System.Data.SqlDbType.Int);
24 System.Data.SqlClient.SqlParameter poffers_new = objCmd.Parameters.Add("@offers_new", System.Data.SqlDbType.Int);
25 System.Data.SqlClient.SqlParameter pinterviews_taken_place_new = objCmd.Parameters.Add("@interviews_taken_place_new", System.Data.SqlDbType.Int);
26 System.Data.SqlClient.SqlParameter pinterviews_arranged_new = objCmd.Parameters.Add("@interviews_arranged_new", System.Data.SqlDbType.Int);
27 System.Data.SqlClient.SqlParameter punique_mailshots_sent_new = objCmd.Parameters.Add("@unique_mailshots_sent_new", System.Data.SqlDbType.Int);
28 System.Data.SqlClient.SqlParameter pmailshots_new = objCmd.Parameters.Add("@mailshots_new", System.Data.SqlDbType.Int);
29 puserid.Value = Convert.ToInt16(userid.Text);
30 pdate.Value = Convert.ToDateTime(date.Text);
31
32 objCmd.ExecuteNonQuery();
33 objConn.Close();
34


 

Thanks in a dvance

 

Dave