1. Displaying Many-to-Many Relationships
2. Reacting to Illegal Row Editing in a DataGrid
3. Reacting to Illegal Row Deletion in a DataGrid
4. How to Make a Non-DataGrid Control Act as the Mast

Comments

1. David Jones
   22 May 2007 at 05:25
   I didn't like any of the solutions to this problem until I came up with this one...
   
   The solution is to bind the entire Child table to a bindingSource and that to a dataGridView.  In this case the child table would be the courses that the soldier registered for.
   
   Then, whenever a soldier is selected, store the selected row in a global variable, such as lastSelectedSoldierRow. Then, when that changes, you do a select on the table that connects the two. The registers table in this case. For example registerDataTable.Select("soldier_ID = " + lastSelectedSoldierRow.ID.ToString());
   
   Take all those rows and add the course Ids to a globally declared stringBuilder. Whenever a different soldier is selected, add -1 to the stringBuilder as an initializer. Then, for each additional course ID added to the stringBuilder, add a comma to the stringBuilder before it. You'll end up with something like "1,2,3,4,5,6". Next, set the child table's bindingSource.Filter to a that string like so: Filter = "ID in (1,2,3,4,5)".
   
   That will filter all the courses, down to the ones which belong to the soldier. Whenever a new course is added, append the ID to the stringBuilder and reset the filter.
   
   Here's an example scrap of source code from my own project. It's messy, but may be helpful to somebody if the above wasn't enough.
   
   StringBuilder settingsFilterSB = new StringBuilder();
           private void dataGridViewComputers_SelectionChanged(object sender, EventArgs e)
           {
               if (this.dataGridViewComputers.SelectedRows.Count == 1 || this.dataGridViewComputers.SelectedCells.Count > 0)
               {
                   object dataBoundItem;
                   if (this.dataGridViewComputers.SelectedRows.Count == 1)
                       dataBoundItem = this.dataGridViewComputers.SelectedRows[0].DataBoundItem;
                   else
                       dataBoundItem = this.dataGridViewComputers.Rows[this.dataGridViewComputers.SelectedCells[0].RowIndex].DataBoundItem;
                   lastSelectedPcRow = (CallistoDataSet.ComputerOrGroupRow)((DataRowView)dataBoundItem).Row;
   
                   settingsFilterSB = new StringBuilder();
                   settingsFilterSB.Append("-1");
                   int selectedPcId = lastSelectedPcRow.ID;
                   foreach(CallistoDataSet.ComputerOrGroup2SettingsRow row in this.callistoDataSet.ComputerOrGroup2Settings.Rows)
                   {
                       if(row.ComputerOrGroup_ID == selectedPcId)
                           settingsFilterSB.Append("," + row.ComputerSettings_ID.ToString());
                   }
                  
                   this.computerSettingsBindingSource.Filter = "ID in (" + settingsFilterSB.ToString() + ")";
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
2. Nick Hrones
   04 Oct 2006 at 14:57

   Use a BindingSource control then use its Find method to get the index of the row.

3. Devin Loiacano
   31 Mar 2006 at 02:50

   I'm getting this error message: "Object reference not set to an instance of an object." when I try to run the code below. I've spent a couple days trying to figure out what it is, but I'm kind of new to vb.net and programming. I have two tables that look something like below (not all fields are shown). They should be related via the userID fields as a "many tasks to each user" relation. Any help on how to do this or why there is an error when I run the code would be greatly appreciated.

    

   Table: Users                        Table:Tasks                  

   userID                                 userID

   userName                           taskID

   password                           taskName

    

   Dim

   connection As New OleDbConnection("Provider=Microsoft.JET.OLEDB.4.0; data source=" & Application.StartupPath & "\blueteam2.mdb")

   Dim adpUsers As New OleDbDataAdapter("SELECT * FROM Users,Tasks,Projects", connection)

   Dim ds As New DataSet

   Try

   adpUsers.Fill(ds, "Users")

   ds.Relations.Add("UserTasks", ds.Tables("Users").Columns("userID"), ds.Tables("Tasks").Columns("userID"))

   dgUsers.SetDataBinding(ds, "Users.userID")

   dgTasks.SetDataBinding(ds, "Tasks.userID")

   Catch ex As Exception

   MessageBox.Show(ex.Message, "Admin Main Form Load")

   End Try

    

4. Josef Meile
   24 Sep 2005 at 18:54
   Well, not really. I'm exagerating a litte bit
   
   Anyway, I just want to thank you for this nice and realy usefull article.
   I not only got the relationships shown in a DataGrid, but also I could
   modify them through the DataSet.
5. Jo_dc
   27 Jul 2005 at 14:46

   try  
   Private view As  DataView = m_ds.Tables("Stuff").DefaultView
   

   
   But anyway I think that the trick is that the field ID is PK

6. grom
   13 Jul 2005 at 22:11

   I tried your code but the dv index is out of sync with the bm index. Please explain. You can email me at glenn_r@shaw.ca.
   

   
   

   
   Here my challenge. I have reference to a datarow in a datatable. I want the set the bindingcontext position to that datarow. How can I do this? When I sort the dataview it goes out of sync with the datatable index returned when I use the dv find method.
   

   
   Thanks,
   Glenn

7. ODINNE MUSA
   04 Mar 2004 at 07:41
   I think the program is cool and understanding
8. Developer Fusion Bot
   01 Jan 1999 at 00:00

   This thread is for discussions of Winforms Data Binding Lessons Learned.