CODEWITHSUNDEEP
wpfbindingcomboboxproperties
WPFNewbie
WPFNewbie

Reputation: 2534

ComboBox using ItemsSource binding affects other properties

I have a combo box that displays a list of available system colors. Each item in the combo box has a preview rectangle and the text color name. At a given time I may need as many as 6 of these combo boxes on the screen at once. I created a static list of items to reuse across all combo boxes to reduce overhead. It works, and it is fast, but now when I change other combo box properties such as setting the font weight to bold, it affects all combo boxes, not just the one I applied the property to.

Here is my code, all done in code behind.

Declaration of the list I reuse and the combo box:

    static private List<ListViewItem> _colorItems = null;
    ComboBox _comboBoxColorList;

Then in the constructor for my control that contains the combo box I have the code for the initial creation of the list:

        if (_colorItems == null)
        {
            _colorItems = new List<ListViewItem>();

            PropertyInfo[] colorProperties = typeof(Colors).GetProperties(BindingFlags.Static | BindingFlags.Public);
            Dictionary<String, Color> colorDictionary = colorProperties.ToDictionary(p => p.Name, p => (Color)p.GetValue(null, null));
            ListViewItem newItem;
            foreach (KeyValuePair<String, Color> keyPair in colorDictionary)
            {
                newItem = CreateListViewItem(keyPair.Key, keyPair.Value);
                _colorItems.Add(newItem);
            }
        }

Then I create the combo box:

        _comboBoxColorList = new ComboBox();
        _comboBoxColorList.Height = Constants.ListViewPropertyComboBoxHeight;
        _comboBoxColorList.VerticalContentAlignment = VerticalAlignment.Center;
        _comboBoxColorList.Background = Brushes.White;
        _comboBoxColorList.ItemsSource = _colorItems;
        _comboBoxColorList.SelectionChanged += new SelectionChangedEventHandler(comboBoxColorList_SelectionChanged);
        Children.Add(_comboBoxColorList);

Then later one in an event handler I have this code to set the combo box to bold:

            _comboBoxColorList.FontWeight = FontWeights.Bold;

If I make it so that _colorItems is not static everythings behaves as it should, but it is slow. When _colorItems is static it is very fast, but the line above makes all combo boxes taht share the item source bold.

Any insight or wisdom would be great.

Upvotes: 1

Views: 1040

Answers (2)

dowhilefor
dowhilefor

Reputation: 11051

Instead of creating ListBoxItems directly, let this be done by the Framework. In fact you do alot in code which can, and should, be done in XAML.

To make it simple:

Create an ObservableCollection with a new class you create, call it maybe ColorInfo add all your properties like name, the real color. And fill this list with all your colors. This can be reused as often as you want.

class ColorInfo
{
    public Color Color{get;set;}
    public string Name{get;set;}
}

ObservableCollection<ColorInfo> myColors;

Now, you set this List as the ItemsSource of your ComboBox. And finally you provide an item template, how each entry should look like.

<ComboBox x:Name="_comboBoxColorList">
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <DockPanel>
            <Rectangle DockPanel.Dock="Left" Width="16" Height="16">
                <Rectangle.Fill>
                    <SolidColorBrush Color="{Binding Color}"/>
                </Rectangle.Fill>
            </Rectangle>
                <TextBlock Fill="{Binding Name}"/>
            </DockPanel>
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>

Of course you could extract the Template and reference it via StaticResource.

Upvotes: 1

brunnerh
brunnerh

Reputation: 184451

If those ListViewItems are the ones from the framework you should not do that. If you have a list that is shared between controls it should only contain data, not UI-elements. If you need the data to be displayed in a certain way use the ItemTemplate and/or the ItemContainerStyle.

See also: Styling and Templating

(Just setting the ItemsSource is not a binding by the way...)

Upvotes: 0

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