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How to open a new WPF user control in a WPF user control? [duplicate]

My goal is to attach a new image control while the application is running.
img = new System.Windows.Controls.Image();
img.Margin = new Thickness(200, 10, 0, 0);
img.Width = 32;
img.Height = 32;
img.Source = etc;
I've tried
this.AddChild(img);// says must be a single element
this.AddLogicalChild(img);// does nothing
this.AddVisualChild(img);// does nothing
It was never this difficult to add a element with forms.
How can I simply attach this new element to the main window (not another control) so that it will show up.
Solved it, I named the grid main, and from there I was able to access the children attribute and the add function
main.children.add(img);
<Window x:Class="Crysis_Menu.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded" AllowsTransparency="False" Background="White" Foreground="{x:Null}" WindowStyle="SingleBorderWindow">
<Grid Name="main">
<Button Content="Run" Height="23" HorizontalAlignment="Left" Margin="12,12,0,0" Name="btnRun" VerticalAlignment="Top" Width="151" Click="btnRun_Click" />
<TextBox Height="259" HorizontalAlignment="Left" Margin="12,40,0,0" Name="tbStatus" VerticalAlignment="Top" Width="151" />
</Grid>
</Window>

You should have only one root element under window. Adding the image using this.AddChilda adds the image as child of window, but you probably have some other child defined(Grid for example). Give a name to this child (Grid in the example) and then in the code behind add the image to the Grid
Example :
<Window>
<Grid x:Name="RootGrid">
</Grid>
</Window>
Then in the code behind use
RootGrid.Children.Add(img);

What is this in your case? You can try this.Content = image; or this.Children.Add(image);
If your this is indeed a Window, you should know that Window can have only a single child, which you put into Content. If you want several items in Window, usually you put some appropriate container (for example, Grid or StackPanel) as Window's content, and add children to it.

Vlad got the solution. I used it :
var grid = this.Content as Grid;
// or any controls
Label lblMessage = new Label
{
Content = "I am a label",
Margin = new Thickness(86, 269, 0, 0)
};
grid.Children.Add(lblMessage);

resize child content of element host with form resize

I am completely new to WPF and have to do a bit of work on it for my job. I have a form which contains 3 element hosts each with their own child controls. I need the child controls to resize with the form so they grow and shrink when the form does.
Only the element hosts themselves seem to have the anchor property which is what I understand I need to manipulate to achieve this. How can I get the child controls to resize as well as the element hosts or am I doing this completely wrong?
Any help would be great.
I've tested with a standard text box control, and setting the Anchor property of that to Top, Left, Bottom works fine. I don't understand why it doesn't work for the element host content
<UserControl x:Class="MyControls.ucEventViewerOptions"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/,arkup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
d:DesignHeight="297" d:DesignWidth="128" Loaded="UserControl_Loaded">
<Grid Width="96" Height="288">
<DataGrid AutoGenerateColumns="False" Height="288" HorizontalAlignment="Left" Name="dgEventViewerOptions" VerticalAlignment="Top" Width="96" SelectionChanged="dgEventViewOptions_SelectionChanged" />
</Grid>
</UserControl>

In WPF, this type of behavior is generally caused by the HorizontalAlignment and VerticalAlignment properties. Ommitting these properties will set them to their default value "Stretch" and allows controls to resize in relation to their parent containers. This is only possible when the controls are not assigned with fixed sizes, though.
In your case, you may simply ommit these properties:
<UserControl x:Class="MyControls.ucEventViewerOptions"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/,arkup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
d:DesignHeight="297" d:DesignWidth="128" Loaded="UserControl_Loaded">
<Grid>
<DataGrid AutoGenerateColumns="False" Name="dgEventViewerOptions" SelectionChanged="dgEventViewOptions_SelectionChanged" />
</Grid>
</UserControl>
Unless you wish them to have a fixed height or width, of course.

If you want items to resize depending on parent elements size, you have to keep in mind that controls are implicitly inheriting parents' stretching behavior when size is not set explicitly. So to fix your problem, you need to remove setting Width and Height explicitly:
<Grid>
<DataGrid AutoGenerateColumns="False" Name="dgEventViewerOptions" SelectionChanged="dgEventViewOptions_SelectionChanged" />
</Grid>

Adding a WPF UserControl programmatically has no style

I'm trying to create a button-like UserControl which consists of a border and a label. When adding this UserControl directly in the XAML of MainWindow, it renders correctly (it is put in a WrapPanel), but if I add it programmatically it doesn't look the same at all. There is no border, no background color, the text size of the label is wrong and so is the text color.
This is my user control:
<UserControl x:Class="Jishi.SonosPartyMode.UserControls.Player"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
d:DesignHeight="150" d:DesignWidth="300"
Width="200"
Height="100">
<Border BorderBrush="#086EAA" CornerRadius="8,8,8,8" BorderThickness="4" Margin="15" Padding="15px" VerticalAlignment="Center" Background="#0A4069">
<Label Name="PlayerName" TextElement.Foreground="White" TextElement.FontSize="20px">asdasdasd</Label>
</Border>
</UserControl>
when adding it, I just invoke it like this:
var button = new Player { Content = player.Properties.RoomName, DataContext = player.Properties.UDN };
PlayerList.Children.Add( button );
PlayerList is the actual WrapPanel and Player is my UserControl. I have tried finding information regarding this, but I don't find anything. If you have another approach that I can take, please come with suggestions. All I want is a clickable area with some rounded corners that can contain text (one or more rows).
I can apply styles programatically, but the styles defined in the xaml for the UserControl isn't preserved (Border, Margins, colors etc).

First of all, you don't need to create a custom control for this, you can easily do
var button = new Border { *border properties*, Content = new Lable {Content="dfsdfsdfsd"}};
And if you use PlayerList.Children.Add( button ); then it adds to the end of Wrappanel and in XAML code you add it not as the last element (maybe)..
And the last idea is that you lost some properties that you added in XAML when test it (like aligment, margin, etc.)
Hope this helps.

displaying a canvas at two positions simultaneously

In C#, using WPF components, Is it possible to display a canvas (whose contents change at run time based on user input) at two positions on the screen? or in two windows? So basically, whatever happens in the canvas positioned at one place happens in the canvas positioned in the other place.

Do you need them both to be interactive?
If not, then you could use a VisualBrush to duplicate the Canvas to another location. The VisualBrush part won't be interactive, but it will mirror what happens on the other one.

So, there are 2 solutions :
create control containing your canvas & add them to required places and bind to your VM
use visualbrush as #Tim mentioned, example:
<Window x:Class="visualbrushmirroringstackoverflow.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<VisualBrush x:Key="MirrorBrush"
Visual="{Binding ElementName=TargetCanvas}" TileMode="None"
Stretch="None" AutoLayoutContent="False"/>
</Window.Resources>
<StackPanel>
<Button Click="Button_Click" Content="Add Random Rects" Margin="5"/>
<Border BorderThickness="1" BorderBrush="Black" Margin="5">
<Canvas x:Name="TargetCanvas" Width="100" Height="100"
Background="White" />
</Border>
<Border BorderThickness="1" BorderBrush="Black" Margin="5">
<Rectangle Width="100" Height="100"
Fill="{StaticResource MirrorBrush}" />
</Border>
</StackPanel>
handler in code behind:
private void Button_Click(object sender, RoutedEventArgs e)
{
var rnd = new Random();
var element = new Rectangle { Fill = Brushes.Black, Width = 5, Height=5 };
Canvas.SetLeft(element, rnd.Next(100));
Canvas.SetTop(element, rnd.Next(100));
TargetCanvas.Children.Add(element);
}

If you're populating and updating the Canvas through databinding, you can create a usercontrol that defines the Canvas and all of it's styles, templates etc and bind each instance of that usercontrol to the same source object. Even in different windows, because they are updating from the same object in memory they should appear synchronised.

I had a same problem where i was asked to display a canvas in other window while retaining the original canvas.
What i did and you can do is this:
Since a single child cannot have multiple parents so you can make a copy of your original by serializing them using XamlReader.Save.
Put this canvas in a ViewBox (so that it stretches to its parent). Set contents of new window as this ViewBox.
Canvas copycanvas = XamlReader.Parse(XamlWriter.Save(OriginalCanvas)) as Canvas;
ViewBox vb = new ViewBox() { Stretch.Uniform, Child = copyCanvas };
Windows newwin = new Window() { Content = vb };
newwin.ShowDialog();

Update UI by code in WPF

I'm trying to update some user control in wpf by code, with no luck.
That's the xaml:
<UserControl x:Class="SimuladorNocs.UI.Diagram.PropertiesWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:PropertyGrid="clr-namespace:Deepforest.WPF.Controls"
>
<DockPanel>
<StackPanel x:Name="stackPanel" Width="300" Height="600" HorizontalAlignment="Center">
<PropertyGrid:PropertyGridControl Height="300" x:Name="MyPropertyGrid" />
</StackPanel>
</DockPanel>
and that's the c# code:
public void SetInstance(object obj){
MyPropertyGrid = new PropertyGridControl { Instance = obj, Height = 300 };
stackPanel.Children.Clear();
stackPanel.Children.Add(MyPropertyGrid); }
In the end, the property appers to be changing, but I was unable to see the changes in the UI. I also tried to create a new object instead of using the existing MyPropertyGrid, did not work, also tried not clearing the stackpanel without success...
What am I missing?
Thanks

stackPanel.InvalidateVisual();
Please add this at the last line.

I don't have the specified propertygrid control but it seems that the UI doesn't get updated. did you try "UpdateLayout()" on that control and on the stack panel itself ?

Swapped out the PropertyGridControl for a Label and it worked fine. I suggest you do the same. If it works, it's more a question of what the PropertyGridControl is doing wrong...