#681 – No Mouse Events When Visibility is Hidden, Collapsed or Hidden

User interface elements will not receive mouse-based events when the element’s Visibility property is Collapsed or Hidden (rather than Visible).

    <StackPanel>
        <Button Content="Visibility = Collapsed" Visibility="Collapsed"
                MouseMove="Button_MouseMove"
                HorizontalAlignment="Center" Margin="5" />
        <Button Content="Visibility = Hidden" Visibility="Hidden"
                MouseMove="Button_MouseMove"
                HorizontalAlignment="Center" Margin="5" />
        <Button Content="Visibility = Visible" Visibility="Visible"
                MouseMove="Button_MouseMove"
                HorizontalAlignment="Center" Margin="5" />
    </StackPanel>

When we move the mouse of the space where the button whose Visibility is Hidden, we don’t see the MouseMove event firing.

#644 – Disabling and Hiding Controls

You can disable a control by setting its IsEnabled property to false.  Disabled controls cannot receive input, but are still displayed in the user interface, typically greyed out.

Below is an example of some typical controls, showing what they looked like when enabled vs. disabled.

In addition to disabling a control, you can also make the entire control invisible, using the Visibility property.  Controls that are not visible can be one of:

  • Hidden – Control is not visible, but it still takes up space in the user interface.  I.e. There is whitespace where the control would be if it were visible
  • Collapsed – Control is not present at all in the user interface and neighboring controls fill in the space where the control would be if it were visible

 

 

#495 – Binding to a Visibility Property Without Using a Value Converter

You can use a value converter to convert a string value to a value of type System.Windows.Visibility, allowing data binding to a Visibility property.  You can also just set a Visibility property directly to a string, avoiding the need for a value converter.

In the example below, we bind to the Content property of a ComboBoxItem, which we access through the SelectedValue property of a ComboBox.  Since Content contains a string, the binding to Visibility works without a conversion.

    <StackPanel>
        <StackPanel Orientation="Horizontal" Margin="10">
            <Label Content="Snoopy" Margin="3" Background="BurlyWood"/>
            <Label Content="Waldo" Margin="3" Background="Thistle"
                   Visibility="{Binding ElementName=cboVisibility, Path=SelectedValue.Content}"/>
            <Label Content="Dagwood" Margin="3" Background="LightGreen"/>
        </StackPanel>
        <ComboBox Name="cboVisibility" HorizontalAlignment="Center" SelectedIndex="0">
            <ComboBox.Items>
                <ComboBoxItem Content="Visible"/>
                <ComboBoxItem Content="Collapsed"/>
                <ComboBoxItem Content="Hidden"/>
            </ComboBox.Items>
        </ComboBox>
        <Label Content="Select visibility of middle Label" HorizontalAlignment="Center"/>
    </StackPanel>

#494 – Using a Value Converter to Bind to a Visibility Property

You can bind the Visibility property of a control to a data item whose type is System.Windows.Visibility.  You can also bind to an item whose type is string, provided that the string values returned represent one of the enumerated values from the Visibility type.

The example below shows how to use a value converter to convert from the SelectedValue of a ComboBox (a ComboBoxItem) to the Visibility type.

        <StackPanel Orientation="Horizontal" Margin="10">
            <Label Content="Snoopy" Margin="3" Background="BurlyWood"/>
            <Label Content="Waldo" Margin="3" Background="Thistle"
                   Visibility="{Binding ElementName=cboVisibility, Path=SelectedValue, Converter={StaticResource cboVisibilityConverter}}"/>
            <Label Content="Dagwood" Margin="3" Background="LightGreen"/>
        </StackPanel>
        <ComboBox Name="cboVisibility" HorizontalAlignment="Center" SelectedIndex="0">
            <ComboBox.Items>
                <ComboBoxItem Content="Visible"/>
                <ComboBoxItem Content="Collapsed"/>
                <ComboBoxItem Content="Hidden"/>
            </ComboBox.Items>
        </ComboBox>

Code for IValueConverter.Convert:

        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            Visibility visibility = Visibility.Visible;

            try
            {
                if (value != null)
                {
                    ComboBoxItem item = (ComboBoxItem)value;
                    visibility = (Visibility)Enum.Parse(typeof(Visibility), (string)item.Content, false);
                }
            }
            catch { }

            return visibility;
        }

#493 – Setting the Visibility of a User Interface Element

You can set the visibility of any element that inherits from UIElement by settings its Visibility property to one of the three values listed below.  Because every child hosted in a panel derives from UIElement, this is how you hide/show child elements in a panel.

Values for Visibility (of type System.Windows.Visibility):

  • Visible – element is displayed
  • Hidden – element is not displayed, but the space where it is located is preserved
  • Collapsed – element is not displayed and space for it is not preserved

Below is an example that lets a user toggle between the three possible values for the Visibility of the middle Label.

    <StackPanel>
        <StackPanel Orientation="Horizontal" Margin="10">
            <Label Content="Snoopy" Margin="3" Background="BurlyWood"/>
            <Label Content="Waldo" Margin="3" Background="Thistle"
                   Visibility="{Binding ElementName=cboVisibility, Path=SelectedValue, Converter={StaticResource cboVisibilityConverter}}"/>
            <Label Content="Dagwood" Margin="3" Background="LightGreen"/>
        </StackPanel>
        <ComboBox Name="cboVisibility" HorizontalAlignment="Center" SelectedIndex="0">
            <ComboBox.Items>
                <ComboBoxItem Content="Visible"/>
                <ComboBoxItem Content="Collapsed"/>
                <ComboBoxItem Content="Hidden"/>
            </ComboBox.Items>
        </ComboBox>
        <Label Content="Select visibility of middle Label" HorizontalAlignment="Center"/>
    </StackPanel>



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