#501 – Sharing an Event Handler Across Multiple Controls, Method II

February 24, 2012 1 Comment

If you want to use an event handler to handle an event originating from several controls, you can specify the handler for each control and then use the RoutedEventArgs.Source property to determine the control that originated the event.

You can also just specify a handler for the Button.Click event on the parent panel that holds all of the buttons.  It will handle all Click events that originate lower down in the visual tree.

    <StackPanel ButtonBase.Click="Button_Click">
        <Button Content="Keaton" HorizontalAlignment="Center" Padding="10,5" Margin="5"/>
        <Button Content="Chaplin" HorizontalAlignment="Center" Padding="10,5" Margin="5"/>
        <Button Content="Arbuckle" HorizontalAlignment="Center" Padding="10,5" Margin="5"/>
    </StackPanel>

The event handler is the same as before–you can check the RoutedEventArgs.Source property to determine the Button that originated the event.

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            // Get at originator of event using RoutedEventArgs.Source property

            Button b = e.Source as Button;
            MessageBox.Show(string.Format("You clicked on {0} button", b.Content));
        }

Filed under Events Tagged with , ,

#500 – Sharing an Event Handler Across Multiple Controls, Method 1

February 23, 2012 4 Comments

You can use the same event handler for more than one control by specifying the handler for each control and pointing to the same event handler code.

In the example below, we have three buttons, each of which wires up a handler for the Click event, but using the same handler (Button_Click).

    <StackPanel>
        <Button Content="Keaton" HorizontalAlignment="Center" Padding="10,5" Margin="5"
                Click="Button_Click"/>
        <Button Content="Chaplin" HorizontalAlignment="Center" Padding="10,5" Margin="5"
                Click="Button_Click"/>
        <Button Content="Arbuckle" HorizontalAlignment="Center" Padding="10,5" Margin="5"
                Click="Button_Click"/>
    </StackPanel>

In the Button_Click event handler, we can check the Source property of the RoutedEventArgs parameter to determine which button sent us the event.

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            // Get at originator of event using RoutedEventArgs.Source property

            Button b = e.Source as Button;
            MessageBox.Show(string.Format("You clicked on {0} button", b.Content));
        }

Filed under Events Tagged with , , ,

#499 – Interacting with the Control That Initiated an Event

February 22, 2012 Leave a Comment

In WPF, you do not have to provide a name for every control in your user interface.  Since so much is accomplished through data binding, you often don’t need to interact with a control at all from your code.

But one scenario where you might want to interact with a control is from an event handler for an event that the control initiated.  Every event handler will have a sender argument that represents the control that fired the event.  You can cast this argument to the appropriate type to get at the original control.

<Button Content="Click Me" HorizontalAlignment="Center" Padding="10,5" Margin="10"
        Click="Button_Click"/>


        private void Button_Click(object sender, RoutedEventArgs e)
        {
            Button b = sender as Button;
            b.Width = b.ActualWidth + 1;
        }

Filed under Controls Tagged with , ,

No Post Today

February 21, 2012 Leave a Comment

2,000 Things / WPF is on hiatus today–back tomorrow.

Filed under Uncategorized

#498 – A List of WPF Blogs and Forums

February 20, 2012 Leave a Comment

Though many WPF bloggers have long since moved on to greener pastures, there are still a few blogs out there that either still have good WPF content or that still blog about WPF/XAML.  Here is a list of the most useful blogs and forums.

Filed under Miscellaneous Tagged with , ,

#497 – Use a UniformGrid to Make a Group of Buttons the Same Size

February 17, 2012 1 Comment

You can use a StackPanel to make its child elements the same size in one of its dimensions.  This is harder to do in the other dimension.

The example below uses a StackPanel to contain some buttons.  They end up the same height, but are still different widths.

You can make the buttons the same height and width using a UniformGrid instead of a StackPanel.

        <UniformGrid DockPanel.Dock="Bottom" Margin="10" Rows="1" HorizontalAlignment="Right"
                    VerticalAlignment="Bottom">
            <Button Grid.Column="0" Content="No" FontSize="18" Margin="5" Padding="6,3"/>
            <Button Grid.Column="1" Content="Yes, Absolutely" Margin="5" Padding="6,3"/>
            <Button Grid.Column="2" Content="Maybe" Margin="5" Padding="6,3"/>
        </UniformGrid>

The UniformGrid will make sure that each cell is the same height and the same width.  This is desirable because you then avoid having to set the button sizes manually.

Filed under Layout Tagged with , , ,

#496 – Using a StackPanel to Make a Group of Buttons the Same Size

February 16, 2012 3 Comments

You’ll often want to stack a group of buttons in a GUI, vertically or horizontally.  You’d typically use a StackPanel to do this.

Let’s say that you want a series of buttons stacked vertically on the right side of a window.

We can use a DockPanel as the main container and add a StackPanel docked on the right and oriented vertically.  But when we do this, the StackPanel expands to fill the available space, as does each Button.

The HorizontalAlignment of the StackPanel defaults to Stretch, as do each of the buttons.  We could set the HorizontalAlignment for each Button to Right, but the buttons now all size to fit their content, which is not quite what we want.

What we really want is for the HorizontalAlignment of each Button to be Stretch, but for the HorizontalAlignment of the StackPanel itself to be Right.  This gives us what we want.

Filed under Layout Tagged with , ,

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

February 15, 2012 1 Comment

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>

Filed under Data Binding Tagged with , ,

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

February 14, 2012 4 Comments

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;
        }

Filed under Data Binding Tagged with , ,

#493 – Setting the Visibility of a User Interface Element

February 13, 2012 1 Comment

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>



Filed under Controls Tagged with , , , , ,

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