Question re:Adding Modifying and Deleting rows in a DataGridView

Question

I have a windows form with Master data - a recipe
and details data - Ingredients, Methods and Preperation

the details are managed in 3 dataGridViews there is a save button which when pressed goes through each of the Recipe, Ingredient, Method and Preperation Data saving changes in turn this allows the user to make a lot of changes for only one save.

This works OK until there are a lot of changes to one table and it appears to get confused when I make changes to a new row which has not got an ID to fetch it seems to change the status of the row from Added to modified.

It is Ok if I only make one or two changes but making a lot causes problems

---

jnc

Answer 1

this is the code for the management of the rows, there must be something missing somewhere or a miss-applied technique

                foreach (DataRow changesRow in dtChanges.Rows)//loop this table
                        { //save the changes UPDATE AND ADD NEW
                            DataRowState rsCh = changesRow.RowState;
                            //MODIFIED but will accept a modified new row
                            if (rsCh == DataRowState.Modified)
                            {
                                 int chVal = 0;
                                if (DBNull.Value.Equals(changesRow["MethodID"]))
                                { //if a new row is also modified it is flagged as modified but has no ID
                                    isnew = true;
                                }
                                else
                                {
                                    chVal = (int)changesRow["MethodID"];
                                }
                                string MO = "";
                                if (!DBNull.Value.Equals(changesRow["MethodOrder"]))
                                {
                                    MO = (string)changesRow["MethodOrder"];
                                }
                                tblMethod tbM = db.tblMethods.SingleOrDefault(m => m.MethodID == chVal);
                                tbM.MethodOrder = MO;
                                string Met = "";
                                if (!DBNull.Value.Equals(changesRow["Method"]))
                                {
                                    Met = (string)changesRow["Method"];
                                }

                                tbM.Method = Met;
                                tbM.BulletType = (int)changesRow["BulletType"];
                                tbM.MethodType = (int)changesRow["MethodType"];//1 =prep or 2 = method
                                if (isnew)
                                {
                                    db.tblMethods.InsertOnSubmit(tbM);
                                }
                            }
                            //ADDED
                            else if (rsCh == DataRowState.Added)
                            {
                                if (!DBNull.Value.Equals(changesRow["Method"]))
                                {//only save if the main field is not empty
                                    string MO = "";
                                    if (!DBNull.Value.Equals(changesRow["MethodOrder"]))
                                    {
                                        MO = (string)changesRow["MethodOrder"];
                                    }

                                    tblMethod tbM = new tblMethod
                                    {
                                        RID = (int)changesRow["RID"],
                                        MethodOrder = MO,
                                        Method = (string)changesRow["Method"],
                                        BulletType = (int)changesRow["BulletType"],
                                        MethodType = (int)changesRow["MethodType"]//1 =prep or 2 = method
                                    };

                                    db.tblMethods.InsertOnSubmit(tbM);
                                }
                            }
                            //DELETED
                            else if (rsCh == DataRowState.Deleted)
                            {
                                DataView cdv = new DataView(dtChanges, "", "", DataViewRowState.Deleted);

                                foreach (DataRowView drv in cdv)
                                {
                                    if (!DBNull.Value.Equals(drv[0]))
                                    {
                                        int chVal = (int)drv[0];
                                        //if (chVal != 0)
                                        {
                                            tblMethod tbM = db.tblMethods.FirstOrDefault(m => m.MethodID == chVal);
                                        db.tblMethods.DeleteOnSubmit(tbM);
                                        }
                                    }
                                    else
                                    {//not previously saved so has no ID
                                        //tblMethod tbM = db.tblMethods.Single();//ch 23/04
                                        tblMethod tbM = db.tblMethods.FirstOrDefault();
                                        db.tblMethods.DeleteOnSubmit(tbM);
                                    }
                                }
                            }
                        }

---

jnc

Answer 2

Hi jnc,

>>if a new row is also modified it is flagged as modified but has no ID.

I'm not sure about it, if there are any changes on the added column, the state is still added. You can try my code here:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            new Program().DemonstrateRowState();
        }
        private  void DemonstrateRowState()
        {
            //Run a function to create a DataTable with one column.
            DataTable myTable = MakeTable();
            DataRow myRow;

            // Create a new DataRow.
            myRow = myTable.NewRow();
            // Detached row.
            Console.WriteLine("New Row " + myRow.RowState);

            myTable.Rows.Add(myRow);
            // New row.
            Console.WriteLine("AddRow " + myRow.RowState);

           // myTable.AcceptChanges();
            // Unchanged row.
         //   Console.WriteLine("AcceptChanges " + myRow.RowState);

            myRow["FirstName"] = "Scott";
            // Modified row.
            Console.WriteLine("Modified, but the state is still " + myRow.RowState);

            myRow.Delete();
            // Deleted row.
            Console.WriteLine("Deleted " + myRow.RowState);
        }

        private DataTable MakeTable()
        {
            // Make a simple table with one column.
            DataTable dt = new DataTable("myTable");
            DataColumn dcFirstName = new DataColumn("FirstName", Type.GetType("System.String"));
            dt.Columns.Add(dcFirstName);
            return dt;
        }

    }
}

BTW, I'm not sure how do you define "isnew" field.

Have a nice day.

---

Alan Chen[MSFT]
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Answer 3

Thanks Alan

As I loop through the changes table I seperate each row into Added, Modified or Deleted but some times if the table has a number of mixed changes like :
1.add a new row,
2.delete another
3.return to the added row and modify

The added row's State is changed to Modified when it is really a NEW row which has been Modified before saving.

Its State should really be Added because when I try to save it is saving as a modifed row with a Zero ID the problem is that sometimes it works OKI hope I have made myself clear

---

jnc