How to display default text “--Select Team --” in

Question

In a WPF app, in MVP app, I have a combo box,for which I display the data fetched from Database. Before the items added to the Combo box, I want to display the default text such as

" -- Select Team --"

so that on pageload it displays and on selecting it the text should be cleared and the items should be displayed.

Selecting data from DB is happening. I need to display the default text until the user selects an item from combo box.

Please guide me

Answer 1

I did it before binding the combobox with data from database in codebehind like this -

Combobox.Items.Add("-- Select Team --");
Combobox.SelectedIndex = 0;

Answer 2

Only set the IsEditable attribute to true

<ComboBox Name="comboBox1"            
          Text="--Select Team--"
          IsEditable="true"  <---- that's all!
          IsReadOnly="true"/>

Answer 3

I would recommend the following:

Define a behavior

public static class ComboBoxBehaviors
{
    public static readonly DependencyProperty DefaultTextProperty =
        DependencyProperty.RegisterAttached("DefaultText", typeof(String), typeof(ComboBox), new PropertyMetadata(null));

    public static String GetDefaultText(DependencyObject obj)
    {
        return (String)obj.GetValue(DefaultTextProperty);
    }

    public static void SetDefaultText(DependencyObject obj, String value)
    {
        var combo = (ComboBox)obj;

        RefreshDefaultText(combo, value);

        combo.SelectionChanged += (sender, _) => RefreshDefaultText((ComboBox)sender, GetDefaultText((ComboBox)sender));

        obj.SetValue(DefaultTextProperty, value);
    }

    static void RefreshDefaultText(ComboBox combo, string text)
    {
        // if item is selected and DefaultText is set
        if (combo.SelectedIndex == -1 && !String.IsNullOrEmpty(text))
        {
            // Show DefaultText
            var visual = new TextBlock()
            {
                FontStyle = FontStyles.Italic,
                Text = text,
                Foreground = Brushes.Gray
            };

            combo.Background = new VisualBrush(visual)
            {
                Stretch = Stretch.None,
                AlignmentX = AlignmentX.Left,
                AlignmentY = AlignmentY.Center,
                Transform = new TranslateTransform(3, 0)
            };
        }
        else
        {
            // Hide DefaultText
            combo.Background = null;
        }
    }
}

User the behavior

<ComboBox Name="cmb" Margin="72,121,0,0" VerticalAlignment="Top"
          local:ComboBoxBehaviors.DefaultText="-- Select Team --"/>

Answer 4

I know this is semi old but what about this way:

<DataTemplate x:Key="italComboWM">
    <TextBlock FontSize="11" FontFamily="Segoe UI" FontStyle="Italic" Text="--Select an item--" />
</DataTemplate>

<ComboBox EmptySelectionBoxTemplate="{StaticResource italComboWM}" />

Answer 5

IceForge's answer was pretty close, and is AFAIK the easiest solution to this problem. But it missed something, as it wasn't working (at least for me, it never actually displays the text).

In the end, you can't just set the "Visibility" property of the TextBlock to "Hidden" in order for it to be hidden when the combo box's selected item isn't null; you have to SET it that way by default (since you can't check not null in triggers, by using a Setter in XAML at the same place as the Triggers.

Here's the actual solution based on his, the missing Setter being placed just before the Triggers:

<ComboBox x:Name="combo"/>
<TextBlock Text="--Select Team--" IsHitTestVisible="False">
    <TextBlock.Style>
        <Style TargetType="TextBlock">

            <Style.Setters>
                <Setter Property="Visibility" Value="Hidden"/>
            </Style.Setters>

            <Style.Triggers>
                <DataTrigger Binding="{Binding ElementName=combo,Path=SelectedItem}" Value="{x:Null}">
                    <Setter Property="Visibility" Value="Visible"/>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </TextBlock.Style>
</TextBlock>

Answer 6

//XAML Code

// ViewModel code

    private CategoryModel _SelectedCategory;
    public CategoryModel SelectedCategory
    {
        get { return _SelectedCategory; }
        set
        {
            _SelectedCategory = value;
            OnPropertyChanged("SelectedCategory");
        }
    }

    private ObservableCollection<CategoryModel> _Categories;
    public ObservableCollection<CategoryModel> Categories
    {
        get { return _Categories; }
        set
        {
            _Categories = value;
            _Categories.Insert(0, new CategoryModel()
            {
                CategoryId = 0,
                CategoryName = " -- Select Category -- "
            });
            SelectedCategory = _Categories[0];
            OnPropertyChanged("Categories");

        }
    }