Update values in datagrid

Posted on 2004-03-28
Last Modified: 2012-06-22
I'm working on Windows Forms Datagrid. I've a datagrid with a Footer row which shows me calculations of the fields I retrieve from database. I want this footer row to be updated whenever I change a value in one of the cells. Can anyone tell me which event i need to override to make this happen. I tried cellChanged() event, but this gets fired even when focus goes into a cell. I need an event to be called only when I "change" something in a cell and swich focus to next cell. Or is there anyway I can call the "Edit" and "Update" functionalities of each row as we do in Web Forms Datagrid (with update and edit button for each row).

Secondly I would like to know how to attach an image icon to the Header text of Column Headers in a WinForm Datagrid.

Question by:lakshmik
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Expert Comment

ID: 10701551
>> I need an event to be called only when I "change" something in a cell and swich focus to next cell.

Private CellValueChanged as Boolean =False ' by default or at first there is no change in any cell  , so set to false
Private _CurrentDGCellLocation as DataGridCell
Private WithEvents _dtDatagridDataSourceTable As DataTable

'Get the DataTable assigned to the DataGrid to a DataTable object declared with events
dtDatagridDataSourceTable  = Me.DataGrid1.DataSource

'Now on the column change of that DataTable set some flag to check if it changed

Private Sub _dtDatagridDataSourceTable _ColumnChanged(ByVal sender As Object, ByVal e As System.Data.DataColumnChangeEventArgs) Handles _dtDatagridDataSourceTable.ColumnChanged

  CellValueChanged  =True

  'Also to get the current cell below code will help u  which can used on when it is changed to other cell to get the
  ' last cell location which is been updated or changed.

        Dim dt As DataTable = CType(sender, DataTable)
        Dim r As DataRow
        Dim c As DataColumn
        Dim row, col As Integer
        row = 0
        col = 0

        'If it is a new row going to be added
        _CurrentDGCellLocation.RowNumber = dt.Rows.Count

        'Find the row location
        For Each r In dt.Rows
            If r Is e.Row Then
                _CurrentDGCellLocation.RowNumber = row
                Exit For
            End If
            row += 1

        'Find the col location
        For Each c In dt.Columns
            If c Is e.Column Then
                _CurrentDGCellLocation.ColumnNumber = col
                Exit For
            End If
            col += 1

End Sub

'Now on the cell changed event of DataGrid
Private Sub DataGrid1_CurrentCellChanged(ByVal sender As Object, ByVal e As EventArgs) handles DataGrid1.CurrentCellChanged
 if CellValueChanged  =true then
  'update ur footer value
  'if u want the last cell which is changed , u can get from the variable "_CurrentDGCellLocation"

 end if

  'set CellValueChanged  to false to initialise for the next event
  CellValueChanged  =false

End Sub

So , the key point is u have to use both the events DataTable coulmnchange event + DataGrid cell change .

Hope this helps u .

- Rajan

Expert Comment

ID: 10701597

'Get the DataTable assigned to the DataGrid to a DataTable object declared with events
_dtDatagridDataSourceTable  = Me.DataGrid1.DataSource


U no need to the get the DataTable from the DataGrid . U will be having it in some DataSet or DataTable Variable already .
(which u would have assigned to the Datagrid)

If u have it as datatable already just include WithEvents Modifier in the declaration of the datatable and make its scope across the form class (as a datamember of the form class and not local to a method/function).

If u have it has only in DataSet , get the DataTable assigned to the Datagrid to a DataTable Vaiable declared as above mentioned and assign the table that u have assigned to Datagrid . ( eg.,_dtDatagridDataSourceTable  = DataSet1.Tables(0))
(or) even u can get it from the datagrid directly  (_dtDatagridDataSourceTable  = Me.DataGrid1.DataSource)


I feel I am explaining it more . Sorry if so ...

Tell if this solution helped .

- Rajan .

Author Comment

ID: 10701646
Hi Rajan,
Thanks a lot for ur help. I'm trying it out now in c#... wil get back once I get it through.
Any idea on attachin ColumnHeader text with an icon for custom sort??

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Expert Comment

ID: 10703018

 u mean to change the
 (^) ascending .
 (V) decending
 icons indicating in the sort column header of a datagrid .

 - Rajan

Author Comment

ID: 10703047
hi Rajan,
I'm implementing custom sorting so that my footer does not get sorted with data everytime. This makes the default icons vanish. So i want to know if there is any way where i can show the user the sorting functionality.


Accepted Solution

pamboo earned 360 total points
ID: 10705404
Sorry , I need more clarification

'Have u made datagrid allowsorting property to false to make column header unaccessable by any user like frozen header .

Then u might be given some button or menu which when user click, it will sort by
the mentioned column of button or menu control.

Now , when after that sorting is made , u need to show in the header of the grid
that this column is sorted by indicating it with normal sort icon in that custom sorted column.

Is this u want ? please let me know . If so then I will check it here and try.

Okay additionaly , to do sorting of a column programatically u can use this below command,

_dtDatagridDataSourceTable.DefaultView.Sort = "[desc] sortcolumnname" ' sort column by decending order
_dtDatagridDataSourceTable.DefaultView.Sort = "sortcolumnname"  'sorting in the other order of the prev

Is the first solution of updated datagrid cell changed helped  ?



Author Comment

ID: 10712659
Thank you for the datagrid cell changed event. It works:).
Abt the column header, I'm first disabling the default feature of sorting for datagrid.
Then i add a bool column(call it "id") with the footer's value alone as false. I then programmatically enable
sorting by handling the mousedown event of datagrid with the following code.
DataGrid.HitTestInfo hti;
                  hti =this.HitTest(e.X, e.Y);
                  string colName;
                  if(hti.Type == DataGrid.HitTestType.ColumnHeader)  
                        int colNum=hti.Column;
                        if(colNum != -1)
                                    dView.Sort = "id Asc," + colName + " desc";      
                                    dView.Sort = "id Asc," + colName + " asc";      
So the sorting is done by cliking the column header but there is no indication if its ascending or descending.
So I want to add a sort icon beside the name of the colm so that i can show if its sorted in ascending or descending.

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