Develop Reference

Element is already the child of another element when doesnt exist?

I'm trying to programatically create a button flyout, within my XAML I have:
<Page.Resources>
<Button x:Key="LaunchFlyout" Content="LAUNCH">
<Button.Flyout>
<Flyout Placement="Top">
<Grid Width="200" Height="200">
<StackPanel>
<Rectangle Fill="Red" Width="100" Height="100" />
<Rectangle Fill="Green" Width="100" Height="100" />
</StackPanel>
</Grid>
</Flyout>
</Button.Flyout>
</Button>
</Page.Resources>
Nested within grids I have:
<Grid x:Name="launchBtn_grid" Grid.Column="1">
</Grid>
And then in my code within the Page_Loaded method I have:
bool hasContainer = localSettings.Containers.ContainsKey("appStatus");
if (!hasContainer) {
Button button = (Button)this.Resources["LaunchFlyout"];
launchBtn_grid.Children.Add(button);
}
else {
Button button = new Button();
button.Content = "LAUNCH";
button.Click += launch_btn_Click;
launchBtn_grid.Children.Add(button);
}
When I debug this, it reaches the IF statement and reaches this line launchBtn_grid.Children.Add(button); and then I get this error Element is already the child of another element.
Does anyone understand why? I have already looked and they dont already exist so I don't understand why it is giving me this error. Does anyone know what I am doing wrong?

I'm not sure in what context/use case your are doing that, but it feels weird to me to have an actual control as a Resource (not a DataTemplate, Style, etc).
If you only want to have 1 button of the 2 different template, why not switch Visibility on the 2 instead of loading controls from your code behind ?
Going forward with the idea, just add both buttons in the Grid within your XAML and switch their Visibility according to the setting you read.
There is a BooleanToVisibilityConverter within the framework to help you with this.

Why do my images show at designtime and not at runtime?

I have a WPF <Image> that I am trying to display on a <Button> inside of a <Toolbar> with the following code.
<ToolBarTray>
<ToolBar Height="26" Name="toolBar1" VerticalAlignment="Top" >
<Button Name="StampButton" Click="StampButton_Click">
<Image Source="/MyApp.Resources;component/Resources/MyImage.png"
Height="16" Width="16" Stretch="Fill"/>
</Button>
</ToolBar>
</ToolBarTray>
The image shows up just fine at design time. However, at runtime nothing is displayed. The resources are in another dll called MyApp.Resources. The button is actually created just fine and the click event works fine also.

Set your image build action to "Resource". Try to use full source path.

I was getting same problem - image displaying at design time, but not at runtime.
I had build action set to resource, tried different pack uris etc etc, but solution was simple
<Window.Resources>
<BitmapImage x:Key="your_image_key" UriSource="your_image.png" />
<Image Source="{StaticResource your_image_key}"/>
</Window.Resources>

This is what worked for me, from a site called wpf-tutorial.com:
<Image Source="/WpfTutorialSamples;component/Images/copy.png" />
Images is a subfolder of the project folder in my case, and I assume also in this sample.

Bing Maps (Silverlight) maps - specifying canvas to be at foreground through XAML

Below is the XAML code i have for a Bing Maps Silverlight weather related implementation.
Here is what i am trying to do:
Have a bing maps with several (over 100) pushpins- on mouseover - show a contentpopup (canvas=myPopup) below. Simple enough.
Everything works fine - however, when mypopup displays on mouseover, it is not on the foreground (the other pins appear on top of the contentpopup) - hence making it not very readable.
Question:
How do i specifiy the myPopup canvas specified in XAML below to always appear in the foreground, i.e. top most of the Bing Maps silverlight control when a user views it on mouseover.
Thanks!
<Grid x:Name="LayoutRoot" Background="White">
<m:Map x:Name="GlobalMap" Mode="Road" Center="15,7" ZoomLevel="2" CredentialsProvider="{StaticResource MyCredentials}" Margin="-70,-40,-100,-72">
<m:MapLayer x:Name="myLayer">
<Canvas x:Name="myPopup" Visibility="Collapsed" Opacity="1">
<Rectangle x:Name="myPopupRectangle" Fill="White" Canvas.Left="0" Canvas.Top="0" Height="100"
Width="100" RadiusX="15" RadiusY="15"/>
<StackPanel Canvas.Left="8" Canvas.Top="8">
<TextBlock x:Name="myPopupTexts" FontSize="5" Width="100">
</TextBlock>
</StackPanel>
</Canvas>
</m:MapLayer>
</m:Map>
</Grid>

Try adding Canvas.ZIndex to the MapLayer element, give it a large value like 200 or add your push pins to another MapLayer (rather than adding the pins directly to the map) that appears ahead of this popup layer in document order.

I did something similar to this, but took a different approach. What I did was create a custom pushpin template and create a PopUp within the template.
When the user hovers over the pushpin, the popup is displayed. Using the PopUp will solve your problem, since the control will automatically position it on top of everything. Try wrapping the Canvas in a PopPup and see if that works.
hth

ControlTemplate

I am quite new to WPF and have a basic question :
Assume the following is xaml declaration in my xaml file
<ContentControl x:Name="interactionActivityContent" Loaded="interactionActivityContent_Loaded">
<shapes:BaseShape.DragThumbTemplate >
<ControlTemplate x:Name="interactionActivityTemplate">
<Grid AllowDrop="True" x:Name="GridTest" >
<Rectangle Name="Interaction" Fill="Yellow" Stroke="Green" StrokeThickness="2" IsHitTestVisible="True" AllowDrop="True"></Rectangle>
<local:DesignerCanvas x:Name="ActivitiesCanvasArea" Margin="1,1,1,1" IsHitTestVisible="True" AllowDrop="True" Background="Blue"></local:DesignerCanvas>
</Grid>
</ControlTemplate>
</shapes:BaseShape.DragThumbTemplate>
*shapes:BaseShape.DragThumbTemplate is coming from some different class.
*DesignerCanvas is my own custom canvas for which I want to set value at run time.
How can I access ActivitiesCanvasArea in my C# code from the code behind file?
Do I need to change the way xaml is declared. I need to apply DragThumbTemplate to my grid so that I can move around grid on main screen.

From http://blogs.msdn.com/b/wpfsdk/archive/2007/03/16/how-do-i-programmatically-interact-with-template-generated-elements-part-i.aspx
If you need to find a named element in the ControlTemplate of myButton1, like the Grid, you can use Template.FindName like so:
// Finding the grid generated by the ControlTemplate of the Button
Grid gridInTemplate = (Grid)myButton1.Template.FindName("grid", myButton1);

How to use a custom item template containing Path tag in ComboBox (without causing out of range exception)

I have a combo box with the following DataTemplate:
<DataTemplate x:Key="ComboBoxDataTemplate">
<StackPanel>
<TextBlock Text="{Binding Path='Name'}"/>
<Path Data="{Binding Path='PathGeometry'}" Width="64" Height="64" Stroke="Black" Stretch="Fill" StrokeThickness="1"/>
</StackPanel>
</DataTemplate>
PathGeometry is something simple like 0,1 0,0.5 0.5,0 0,1 (a simple curve). When I select the item in my combo box, the whole silverlight app goes white. An exception is thrown "Value is out of range", which I handle, but then it goes white after that.
Why is the exception thrown? If I remove the {Binding} from the Path tag, and define my own it works fine. It's just the data binding for some reason.

I haven't exactly found "an answer" for this, but I have found a work around.
Rather than building up a property of type PathGeometry, if you change the property to use a String that will work equally well (using the path markup syntax).