Question

I have a custom control that is based off the gridview control located at: here

The control is basically a gridview that automatically creates a column of checkboxes that can be used to “check” individual rows in the gridview.
During the gridview’s “CreateColumns” event, the “checkboxcolumn” is created dynamically. The checkboxcolumn also contains another checkbox in the header that is used to “select/deselect all” checkboxes in the column.

Since the gridview does not automatically remember the state of the checkboxes in the checkboxcolumn on postback, I added a method to the control called “SaveCheckBoxState” which stores the indexes of the checked rows in Viewstate, and then I modified the “OnRowDataBound” event to check the Viewstate and reset the checkboxes based on the Viewstate.

I then added a call to “SaveCheckBoxState” in the gridview’s OnSorting and OnPageIndexChanging events. This works great so long as I’m sorting or changing pages.

However, I need it to update the viewstate everytime someone clicks or unclicks one of the checkboxes. At this time, the checkboxes are rendered with an onclick event that calls some javascript to highlight the row, or in the case of the checkbox in the header, to select/deselect all checkboxes.

I need to call the “SaveCheckBoxState” method from the javascript used by the customcontrol, or I need to find a way to modify viewstate from javascript and perform the same action as “SaveCheckBoxState”.

I’ve tried adding the “SaveCheckBoxState” to the onclick event declaration in the checkboxes, but when run, it simply tells me that the method is undefined. It doesn’t exist in the parent page, and I don’t think I should have to make an event for the parent page to pass the click to. It seems to me this should be all self contained within the custom control.

Does anyone know how I can acheive this?

Here is the code for the gridview OnPreRender event where the onclick event of the checkbox is set:

protected override void OnPreRender(EventArgs e)
        {
            // Do as usual
            base.OnPreRender(e);

            // Adjust each data row
            foreach (GridViewRow r in Rows)
            {
                // Get the appropriate style object for the row
                TableItemStyle style = GetRowStyleFromState(r.RowState);

                // Retrieve the reference to the checkbox
                CheckBox cb = (CheckBox)r.FindControl(InputCheckBoxField.CheckBoxID);

                // Build the ID of the checkbox in the header
                string headerCheckBoxID = String.Format(CheckBoxColumHeaderID, ClientID);

                // Add script code to enable selection
                cb.Attributes["onclick"] = String.Format("ApplyStyle(this, '{0}', '{1}', '{2}')",
                            SelectedRowStyle.CssClass,
                            style.CssClass,
                            headerCheckBoxID);

                // Update the style of the checkbox if checked
                if (cb.Checked)
                {
                    r.BackColor = SelectedRowStyle.BackColor;
                    r.ForeColor = SelectedRowStyle.ForeColor;
                    r.Font.Bold = SelectedRowStyle.Font.Bold;
                }
                else
                {
                    r.BackColor = style.BackColor;
                    r.ForeColor = style.ForeColor;
                    r.Font.Bold = style.Font.Bold;
                }
            }
        }

Answer 1

You should have your custom GridView control subscribe to the CheckChanged event of the checkboxes. It should call its SaveCheckBoxState method on its own. That method should be private.

Parent and child controls should only communicate via properties and events, never through methods and fields.