Question

I am having a problem with the handling of an index changed event for a comboBox that resides inside a dataGridView. I write an method to handle the comboBox selection change using either a delegate:

ComboBox.SelectedIndexChanged -= delegate { ComboBoxIndexChanged(); };
ComboBox.SelectedIndexChanged += delegate { ComboBoxIndexChanged(); };

or an EventHandler:

comboBox.SelectedIndexChanged += new EventHandler(ComboBoxIndexChanged);

but both methods do not work as expected. That is, when you click on your selection within the comboBox (contained within the dataGridView) it takes multiple clicks to cause my ComboBoxIndexChanged(); method to function proper, that if it decides to function at all. What is the best way to overcome/go-about specifying an event on an indexedChange of a comboBox within a dataGridView?

The code I am currently using in context is as follows:

private void dataGridView_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
{
    try
    {
        if (this.dataGridView.CurrentCell.ColumnIndex == (int)Column.Col)
        {
            ComboBox comboBox = e.Control as ComboBox;
            if (comboBox != null)
            {
                comboBox.SelectedIndexChanged += new EventHandler(ComboBoxIndexChanged);
            }
        }
        return;
    }
    catch (Exception Ex)
    {
        Utils.ErrMsg(Ex.Message);
        return;
    }
}

and the event ComboBoxIndexChanged is:

private void ComboBoxIndexChanged(object sender, EventArgs e)
{
    // Do some amazing stuff...
}

I have read a similar thread on StackOverFlow which states that there is a problem with dealing with the comboBox change event this way, but I cannot get the solution to work. The post can be found here: "SelectedIndexChanged" event in ComboBoxColumn on Datagridview. It says:

“Things get complicated since they optimized the DataGridView by only having one editing control for all the rows. Here’s how I handled a similar situation:

First hook up a delegate to the EditControlShowing event:

myGrid.EditingControlShowing += new DataGridViewEditingControlShowingEventHandler(
                                Grid_EditingControlShowing);
...

Then in the handler, hook up to the EditControl’s SelectedValueChanged event:

void Grid_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
{
    ComboBox combo = e.Control as ComboBox;
    if (combo != null)
    {
        // the event to handle combo changes
        EventHandler comboDelegate = new EventHandler(
          (cbSender, args) =>
            {
                DoSomeStuff();
            });

        // register the event with the editing control
        combo.SelectedValueChanged += comboDelegate;

        // since we don't want to add this event multiple times, when the 
        // editing control is hidden, we must remove the handler we added.
        EventHandler visibilityDelegate = null;
        visibilityDelegate = new EventHandler(
          (visSender, args) =>
            {
                // remove the handlers when the editing control is
                // no longer visible.
                if ((visSender as Control).Visible == false)
                {
                    combo.SelectedValueChanged -= comboDelegate;
                    visSender.VisibleChanged -= visibilityDelegate;
                }
            });

         (sender as DataGridView).EditingControl.VisibleChanged += 
           visibilityDelegate;
    }
}"

This issue I have with this is that “VisSender” is not defined hence the event “VisibleChanged” cannot be used.

Any help from you lads, is as always, most appreciated.

Answer 1

Sounds like you want the changes to be committed as soon as the user changes the drop down box, without them having to click off of the cell. In order to do this you will need to force the commit when the change happens (using CommitEdit, there is also an example on the MSDN page). Add this to your DataGridView:

// This event handler manually raises the CellValueChanged event
// by calling the CommitEdit method.
void dataGridView1_CurrentCellDirtyStateChanged(object sender,
    EventArgs e)
{
    if (dataGridView1.IsCurrentCellDirty)
    {
        dataGridView1.CommitEdit(DataGridViewDataErrorContexts.Commit);
    }
}

Then you could just listen for the CellValueChanged and avoid having to try and register for the ComboBoxValueChanged event on the underlying editing control.