CODEWITHSUNDEEP
c#wpfdatagridcombobox
FrancescoDS
FrancescoDS

Reputation: 995

WPF datagrid combobox column: how to manage event of selection changed?

I have a datagrid, with a combobox column

<DataGridComboBoxColumn x:Name="DataGridComboBoxColumnBracketType" Width="70" Header="Tipo di staffa" SelectedValueBinding="{Binding type, UpdateSourceTrigger=PropertyChanged}">                    
            </DataGridComboBoxColumn>

I want an event that is fired only when the user changes the value into the combobox. How can I resolve this?

Upvotes: 12

Views: 21658

Answers (4)

Jaydek
Jaydek

Reputation: 57

The problem of getting SelectionChanged events to fire on DataGridComboBoxColumn cells was one that plagued me recently. I used the following solution:

 private void DataGridView_PreparingCellForEdit(object sender, DataGridPreparingCellForEditEventArgs e)
    {
        if (e.Column.DisplayIndex == 3) //Use this IF statement to specifiy which combobox columns you want to attach the event to.
        {
            ComboBox? cb = e.EditingElement as ComboBox;
            if (cb != null)
            {
                // As this event fires everytime the user starts editing the cell you need to dettach any previously attached instances of "My_SelectionChanged", otherwise you'll have it firing multiple times.
                cb.SelectionChanged -= My_SelectionChanged;
                // now re-attach the event handler.
                cb.SelectionChanged += My_SelectionChanged;
            }
        }
    }

Then set up your custom SelectionChanged event handler to whatever you need:

private void My_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        // Your event code here...
    }

Upvotes: 2

Mr Rubix
Mr Rubix

Reputation: 1519

To Complete Kevinpo answer, for the code behind you should add some protection because the selectionChanged event is triggered 2 time with a datagridcolumncombobox:

1) first trigger : when you selected a new item

2) Second trigger : when you click on an other datagridcolumn after you selected a new item

The problem is that on the second trigger the ComboBox value is null because you don't have changed the selected item.

private void SomeSelectionChanged(object sender, SelectionChangedEventArgs e)
{
    var comboBox = sender as ComboBox;
    if (comboBox.SelectedItem != null)
    {
        YOUR CODE HERE
    }
}

That was my problem, I wish it will help someone else !

Upvotes: 5

Kaloyan Penov
Kaloyan Penov

Reputation: 81

And the xaml code provided by @kevinpo from CodePlex and help from David Mohundro's blog, programatically: 

var style = new Style(typeof(ComboBox));
style.Setters.Add(new EventSetter(ComboBox.SelectionChangedEvent, new SelectionChangedEventHandler(SomeSelectionChanged)));
dataGridComboBoxColumn.EditingElementStyle = style;

Upvotes: 6

kevinpo
kevinpo

Reputation: 1963

I found a solution to this on CodePlex. Here it is, with some modifications:

<DataGridComboBoxColumn x:Name="Whatever">                    
     <DataGridComboBoxColumn.EditingElementStyle>
          <Style TargetType="{x:Type ComboBox}">
               <EventSetter Event="SelectionChanged" Handler="SomeSelectionChanged" />
          </Style>
     </DataGridComboBoxColumn.EditingElementStyle>           
</DataGridComboBoxColumn>

and in the code-behind:

private void SomeSelectionChanged(object sender, SelectionChangedEventArgs e)
{
     var comboBox = sender as ComboBox;
     var selectedItem = this.GridName.CurrentItem;

}

Upvotes: 22

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