I am using C# and developing a winform application. I have a project class which has the project attributes.

the constructor of the project class is as follows:

newProject = new Project(GCD_ID.IsNull() ? (int?)null : Convert.ToInt32(GCD_ID), txt_Proj_Desc.Text, txt_Prop_Name.Text, ST.ID.ToString().IsNull() ? null: ST.ID.ToString(), cmbCentre.Text, 
                                     SEC.ID.ToString().IsNull() ? null : SEC.ID.ToString(), cmbZone.Text,
                                     FD.ID.ToString().IsNull() ? null : FD.ID.ToString(), DT.ID.ToString().IsNull() ? null : DT.ID.ToString(), OP.ID.ToString().IsNull() ? null : OP.ID.ToString(), T.ID.ToString().IsNull() ? null : T.ID.ToString(),
                                     CKV.ID.ToString().IsNull() ? null : CKV.ID.ToString(), STAT.ID.ToString().IsNull() ? null : STAT.ID.ToString(), MW.IsNull() ? (Double?)null : Convert.ToDouble(MW),
                                     txt_Subject.Text, Ip_Num.IsNull() ? (int?)null : Convert.ToInt32(Ip_Num), H1N_ID.IsNull() ? (int?)null : Convert.ToInt32(H1N_ID), 
                                     NOMS_Slip_Num.IsNull() ? (int?)null : Convert.ToInt32(NOMS_Slip_Num), NMS_Updated.IsNull() ? (DateTime?)null : Convert.ToDateTime(NMS_Updated),
                                     Received_Date.IsNull() ? (DateTime?)null : Convert.ToDateTime(Received_Date), Actual_IS_Date.IsNull() ? (DateTime?)null : Convert.ToDateTime(Actual_IS_Date),
                                     Scheduled_IS_Date.IsNull() ? (DateTime?)null : Convert.ToDateTime(Scheduled_IS_Date), UpSt.ID.ToString().IsNull() ? null : UpSt.ID.ToString(),
                                     UpFd.ID.ToString().IsNull() ? null : UpFd.ID.ToString(), txtHVCircuit.Text, cmbbxSIA.Text);

My problem is that i cannot insert values into the database when the datetime variables and the integer variables are null. all this data are assigned to the variable from textboxes on the form..

bELOW is the database function which takes in all the variables and insert them into the database.

public static void createNewProject(int? GCD_ID, string Project_Desc, string Proponent_Name, int Station_ID, string OpCentre, int Sector_ID, string PLZone, int Feeder, int DxTx_ID, int OpControl_ID, int Type_ID, int ConnKV_ID, int Status_ID, double? MW, string Subject, int? Ip_Num, int? H1N_ID, int? NOMS_Slip_Num, DateTime? NMS_Updated, DateTime? Received_Date, DateTime? Actual_IS_Date, DateTime? Scheduled_IS_Date, int UP_Station_ID, int UP_Feeder_ID, string @HV_Circuit, string SIA_Required)
    {
        SqlConnection conn = null;
        try
        {
            //Takes in all the employee details to be added to the database.
            conn = new SqlConnection(databaseConnectionString);
            conn.Open();
            SqlCommand cmd = new SqlCommand("createNewProject", conn);
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.Add(new SqlParameter("GCD_ID", GCD_ID));
            cmd.Parameters.Add(new SqlParameter("Project_Desc", MiscFunctions.Capitalize(Project_Desc)));
            cmd.Parameters.Add(new SqlParameter("Proponent_Name", MiscFunctions.Capitalize(Proponent_Name)));
            cmd.Parameters.Add(new SqlParameter("Station_ID", Station_ID));
            cmd.Parameters.Add(new SqlParameter("OpCentre", OpCentre));
            cmd.Parameters.Add(new SqlParameter("Sector_ID", Sector_ID));
            cmd.Parameters.Add(new SqlParameter("PLZone", PLZone));
            cmd.Parameters.Add(new SqlParameter("Feeder", Feeder));
            cmd.Parameters.Add(new SqlParameter("DxTx_ID", DxTx_ID));
            cmd.Parameters.Add(new SqlParameter("OpControl_ID", OpControl_ID));
            cmd.Parameters.Add(new SqlParameter("Type_ID", Type_ID));
            cmd.Parameters.Add(new SqlParameter("ConnKV_ID", ConnKV_ID));
            cmd.Parameters.Add(new SqlParameter("Status_ID", Status_ID));
            cmd.Parameters.Add(new SqlParameter("MW", MW));
            cmd.Parameters.Add(new SqlParameter("Subject", Subject));
            cmd.Parameters.Add(new SqlParameter("Ip_Num", Ip_Num));
            cmd.Parameters.Add(new SqlParameter("H1N_ID", H1N_ID));
            cmd.Parameters.Add(new SqlParameter("NOMS_Slip_Num", NOMS_Slip_Num));
            cmd.Parameters.Add(new SqlParameter("NMS_Updated", NMS_Updated));
            cmd.Parameters.Add(new SqlParameter("Received_Date", Received_Date));
            cmd.Parameters.Add(new SqlParameter("Actual_IS_Date", Actual_IS_Date));
            cmd.Parameters.Add(new SqlParameter("Scheduled_IS_Date", Scheduled_IS_Date));
            cmd.Parameters.Add(new SqlParameter("UP_Station_ID", UP_Station_ID));
            cmd.Parameters.Add(new SqlParameter("UP_Feeder_ID", UP_Feeder_ID));
            cmd.Parameters.Add(new SqlParameter("HV_Circuit", HV_Circuit));
            cmd.Parameters.Add(new SqlParameter("SIA_Required", SIA_Required));
            cmd.ExecuteNonQuery();
        }
        catch (Exception e) //returns if error incurred.
        {
            MessageBox.Show("Error occured in createNewProject" + Environment.NewLine + e.ToString());
        }
        finally
        {
            if (conn != null)
            {
                conn.Close();
            }
        }
    }

My question is, how do i insert values into the database. please please help