UserControl using parent elements in wpf?

Question

When you have a usercontrol in wpf can it reach outside to its parent elements? For instance my user control just lists some generic things which are held inside the control which is encapsulated within a dockpanel on the main window, but I have a textbox and button in the main window that I would like to access from the control... is this possible?

It would save me alot of time rather than changing the content of the entire window and displaying the same textbox/button in every usercontrol. If anyone has an example of this it would be much appreciated.

Answer 1

Yes it is possible and here is some code I have used to compose presentations out of UserControls that have DPs.

I don't love it even a little, but it works. I also think this is a great topic and maybe some code will help get some better answers!

Cheers,
Berry

UserControl XAML

<Button x:Name="btnAddNewItem" Style="{StaticResource blueButtonStyle}" >
    <StackPanel Orientation="Horizontal">
        <Image Source="{resx:Resx ResxName=Core.Presentation.Resources.MasterDetail, Key=bullet_add}" Stretch="Uniform" />
        <Label x:Name="tbItemName" Margin="5" Foreground="White" Padding="10, 0">_Add New [item]</Label>
    </StackPanel>
</Button>

UserControl Code Behind

public partial class AddNewItemButton : UserControl
{
    ...

    #region Item Name

    public static readonly DependencyProperty ItemNameProperty = DependencyProperty.Register(
        "ItemName", typeof(string), typeof(AddNewItemButton),
        new FrameworkPropertyMetadata(OnItemNameChanged));

    public string ItemName
    {
        get { return (string)GetValue(ItemNameProperty); }
        set { SetValue(ItemNameProperty, value); }
    }

    public string ButtonText { get { return (string) tbItemName.Content; } }

    private static void OnItemNameChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
    {
        // When the item name changes, set the text of the item name
        var control = (AddNewItemButton)obj;

        control.tbItemName.Content = string.Format(GlobalCommandStrings.Subject_Add, control.ItemName.Capitalize());
        control.ToolTip = string.Format(GlobalCommandStrings.Subject_Add_ToolTip, control.ItemName);
    }

    #endregion

    #region Command

    public static readonly DependencyProperty CommandProperty = DependencyProperty.Register(
        "Command", typeof(ICommand), typeof(AddNewItemButton),
        new FrameworkPropertyMetadata(OnCommandChanged));

    public ICommand Command
    {
        get { return (ICommand)GetValue(CommandProperty); }
        set { SetValue(CommandProperty, value); }
    }

    private static void OnCommandChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
    {
        // When the item name changes, set the text of the item name
        var control = (AddNewItemButton)obj;
        control.btnAddNewItem.Command = control.Command;
    }

    #endregion

}

Another UserControl showing Composition

<UserControl ...
         xmlns:uc="clr-namespace:Smack.Core.Presentation.Wpf.Controls.UserControls" 
         >

    <DockPanel LastChildFill="True">
        ...
        <uc:AddNewItemButton x:Name="_addNewItemButton" Margin="0,0,10 0" DockPanel.Dock="Right"  />
        ...
    </DockPanel>
</UserControl>

Answer 2

A better design pattern would be to have the usercontrol notify (via event) the main window when something needs to be changed, and to ask the window (via method) when it needs some information. You would, for example, have a GetText() method on the window that the usercontrol could call, and a ChangeText event on the usercontrol that the window would subscribe to.

The idea is to keep the window in control at all times. Using this mentality will make it easier for you to develop applications in the future.