Hi

I have a DataGrid with 2 columns and one of them is a ComboBoxColumn. I have
implemented re-ordering of rows as described in
windowsclient.net/samples//Go%20To%20Market/DataGridView/DataGridView%
If I have selected a value in the ComboBoxColumn and then move that row to a
new position then the selected value in the ComboBoxColumn is not shown.
Instead the underlying datatype - System.Data.DataRow - is shown. How can I
fix that ?


LookupTable is a DataTable. The 2 most relevant methods are listed below.

private void Form1_Load(object sender, EventArgs e)
{
this.dataGridView1.RowCount = 3;

DataColumn col = new DataColumn("ID", typeof(Int32));
this.LookupTable.Columns.Add(col);
col = new DataColumn("Name", typeof(string));
this.LookupTable.Columns.Add(col);
DataRow row = this.LookupTable.NewRow();
row[0] = 1;
row[1] = "aa";
this.LookupTable.Rows.Add(row);
row = this.LookupTable.NewRow();
row[0] = 2;
row[1] = "bb";
this.LookupTable.Rows.Add(row);

DataGridViewComboBoxColumn c = this.dataGridView1.Columns[0] as
DataGridViewComboBoxColumn;
if (null == c)
return;
// bind the DataGridViewComboBoxColumn to the DataTable
(this.dataGridView1.Columns[0] as
DataGridViewComboBoxColumn).DataSource = this.LookupTable;
(this.dataGridView1.Columns[0] as
DataGridViewComboBoxColumn).ValueMember = "ID";
(this.dataGridView1.Columns[0] as
DataGridViewComboBoxColumn).DisplayMember = "Name";

}

private void dataGridView1_DragDrop(object sender, DragEventArgs e)
{
// The mouse locations are relative to the screen, so they must
be
// converted to client coordinates.
Point clientPoint = this.dataGridView1.PointToClient(new
Point(e.X, e.Y));

// Get the row index of the item the mouse is below.
rowIndexOfItemUnderMouseToDrop =
this.dataGridView1.HitTest(clientPoint.X,
clientPoint.Y).RowIndex;

// If the drag operation was a move then remove and insert the
row.
if (e.Effect == DragDropEffects.Move)
{
DataGridViewRow row =
e.Data.GetData(typeof(DataGridViewRow)) as DataGridViewRow;
try
{
DataRow rowToMove = this.LookupTable.Rows[row.Index];
DataRow newRow = this.LookupTable.NewRow();
newRow.ItemArray = rowToMove.ItemArray;

this.LookupTable.Rows.RemoveAt(row.Index);
this.LookupTable.Rows.InsertAt(newRow,
rowIndexOfItemUnderMouseToDrop);


dataGridView1.Rows.Insert(rowIndexOfItemUnderMouse ToDrop, rowToMove);

this.dataGridView1.Refresh();
}
catch (Exception ex)
{

System.Diagnostics.Trace.WriteLine("dataGridView1_ DragDrop failed: " +
ex.ToString());
}
}
}

--
Paul S

Hi Paul,

I notice that you may mistake DataRow in the Lookup table with the
DataGridViewRow in the DataGridView in the following lines of code, which
are not the same thing:

private void dataGridView1_DragDrop(object sender, DragEventArgs e)
{
...
try
{
DataRow rowToMove = this.LookupTable.Rows[row.Index];
DataRow newRow = this.LookupTable.NewRow();
newRow.ItemArray = rowToMove.ItemArray;

this.LookupTable.Rows.RemoveAt(row.Index);
this.LookupTable.Rows.InsertAt(newRow,
rowIndexOfItemUnderMouseToDrop);


dataGridView1.Rows.Insert(rowIndexOfItemUnderMouse ToDrop, rowToMove);

this.dataGridView1.Refresh();
}
....
}

You should remove the DataGridViewRow being dragged from the DataGridView
first and insert this DataGridViewRow into the new index. Modifiying the
above code as follows should solve the problem:

private void dataGridView1_DragDrop(object sender, DragEventArgs e)
{
...
try
{
this.dataGridView1.Rows.Remove(row);

this.dataGridView1.Rows.Insert(rowIndexOfItemUnder MouseToDrop, row);
}
....
}

If the problem is still not solved, please send me a simple project that
could just reproduce the problem. To get my actual email address, remove
'online' from my displayed email address.

Sincerely,
Linda Liu
Microsoft Online Community Support

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Hi Linda
That works.
Just to point out what did it, compared to the FAQ, where I got the original
solution from - the difference is:

dataGridView1.Rows.Remove(gridRowToMove); // works
//dataGridView1.Rows.RemoveAt(rowIndexOfItemUnderMou seToDrop); does not work.

When I started moving the rows around I had errors with an uncommitted row.
This happened when I moved the last row or when I moved a row below the last
one.
I my case I could solve this by:

this.dataGridView1.AllowUserToAddRows = false;
this.dataGridView1.AllowUserToDeleteRows = false;

The root of the problem was the last un-commited row added by the grid when
the user was allowed to add rows.

Thanks again Linda.
--
Paul S

I works as I wrote in my last mail, but when the control is databound
I get the error:

Rows cannot be programmatically added to the DataGridView's rows collection
when the control is data-bound.

--
Paul S

Hi Paul,

Thank you for your reply!


Yes, you're right. We cannot remove the new row or insert a DataGridViewRow
after the new row in a DataGridView. As you said, the solution is to set
the AllowUserToAddRows property of the DataGridView to true.


No, we cannot add or remove a DataGridViewRow programmtically to a
DataGridView when this DataGridView is data-bound. To do this, you may
exchange the rows in the underlying data source instead. The following is a
sample:

DataRow row = dataTable1.Rows[0];
DataRowState rowstate = row.RowState;
object[] itemarray = row.ItemArray;
dataTable1.Rows.Remove(row);
row.ItemArray = itemarray;

this.LookupTable.Rows.InsertAt(row, 1);
if (rowstate == DataRowState.Added)
{
row.SetAdded();
}
else if (rowstate == DataRowState.Modified)
{
row.SetModified();
}
else if (rowstate == DataRowState.Unchanged)
{
row.AcceptChanges();
}

Hope this helps.
If you have anything unclear, please feel free to let me know.

Sincerely,
Linda Liu
Microsoft Online Community Support

Hi Paul,

Sorry that I made a mistake in my previous reply.

The line of code
this.LookupTable.Rows.InsertAt(row, 1);
should be
dataTable1.Rows.InsertAt(row, 1);


Sincerely,
Linda Liu
Microsoft Online Community Support

Hi Linda

At first I couldn't get it to work - then I deleted the part I didn't
understand - the RowState stuff - now it seems to work and it looks like this:

private void dgvLookup_DragDrop(object sender, DragEventArgs e)
{
// The mouse locations are relative to the screen, so they must
be
// converted to client coordinates.
Point clientPoint = this.dgvLookup.PointToClient(new Point(e.X,
e.Y));

// Get the row index of the item the mouse is below.
rowIndexOfItemUnderMouseToDrop =
this.dgvLookup.HitTest(clientPoint.X, clientPoint.Y).RowIndex;

// If the drag operation was a move then remove and insert the
row.
if (e.Effect == DragDropEffects.Move)
{
DataGridViewRow gridRow =
e.Data.GetData(typeof(DataGridViewRow)) as DataGridViewRow;

DataRow rowToMove = dataTable1.Rows[gridRow.Index];
object[] itemarray = rowToMove.ItemArray;
dataTable1.Rows.Remove(rowToMove);
rowToMove.ItemArray = itemarray;

dataTable1.Rows.InsertAt(rowToMove,
rowIndexOfItemUnderMouseToDrop);
}
}


--
Thanks a lot again Linda.
Paul S