A Better Way
We will derive a new class from DataGrid, called ConfirmDelDataGrid. The derived
class will internally handle the code to attach the javascript attributes.
In order to take advantage of deletion confirmation, the page class merely
has to create an instance of ConfirmDelDataGrid and do nothing else.
Creating a Derived DataGrid
To create the new customized DataGrid, right click on your project in the
Class View and select "Add... Class". You must be in the class view! If
you try this in the solution explorer, you can only add generic classes to
your project. Type a class name and then switch to the Base Class panel. Select
the DataGrid as your base class, like this:
Once you have added your new derived class, we will go about customizing the
behavior. First we need a way to determine which column is the Delete column
in the grid. One approach is to override the DataGrid's CreateColumnSet method
and examine the columns as they are created:
// Class member that stores
the index of the "Delete" column of this grid
protected int delcol = -1;
protected override ArrayList CreateColumnSet(PagedDataSource
dataSource, bool useDataSource)
{
// Let the DataGrid create the columns
ArrayList list = base.CreateColumnSet (dataSource, useDataSource);
// Examine
the columns
delcol=0;
foreach (DataGridColumn col in list)
{
// If this column is the "Delete" button command column...
if ((col is ButtonColumn) && (((ButtonColumn)col).CommandName == "Delete"))
{
// Found it
break;
}
delcol++;
}
// If we did not find a delete column, invalidate the index
if (delcol == list.Count) delcol = -1;
// Done
return list;
}
By overriding the CreateColumnSet method we get a chance to examine the columns
right after they are created by the DataGrid base class. We figure out which
column (if any) is the "Delete" column and store that index in a
protected member variable.
Next we will override the OnItemDataBound method of the DataGrid base class.
First we let the DataGrid bind the item, then we attach the javascript to
the delete column (if any):
// Property to enable/disable deletion confirmation
protected bool confirmdel = true;
public bool ConfirmOnDelete
{
get { return confirmdel; }
set { confirmdel = value; }
}
protected override void OnItemDataBound(DataGridItemEventArgs e)
{
// Create it first in the DataGrid
base.OnItemDataBound (e);
// Attach javascript confirmation to the delete button
if ((confirmdel) && (delcol != -1))
{
e.Item.Cells[delcol].Attributes.Add("onclick", "return confirm('Are
you sure?')");
}
}
So that is the code internal to the DataGrid. Notice that the new behavior
is built-in to the class and a Page object who uses the class does not need
to do anything to enable the deletion confirmation message box.