WPF Canvas, how to add children dynamically with MVVM code behind

ItemsControl is your friend:

<Grid>    <Image Source="..."/>    <ItemsControl ItemsSource="{Binding Points}">        <ItemsControl.ItemsPanel>            <ItemsPanelTemplate>                <Canvas/>            </ItemsPanelTemplate>        </ItemsControl.ItemsPanel>        <ItemsControl.ItemContainerStyle>            <Style>                <Setter Property="Canvas.Left" Value="{Binding X}"/>                <Setter Property="Canvas.Top" Value="{Binding Y}"/>            </Style>        </ItemsControl.ItemContainerStyle>        <ItemsControl.ItemTemplate>            <DataTemplate>                <Border BorderBrush="Red" BorderThickness="1" Width="{Binding Width}" Height="{Binding Height}"/>            </DataTemplate>        </ItemsControl.ItemTemplate>    </ItemsControl></Grid>

The above assumes your VM exposes a collection of points via a Points property, and that each point VM has X, Y, Width, and Height properties.

Added IsItemsHost="True" to the Canvas of Kent's solution:

<Grid>    <Image Source="..."/>    <ItemsControl ItemsSource="{Binding Points}">        <ItemsControl.ItemsPanel>            <ItemsPanelTemplate>                <Canvas  IsItemsHost="True"/>            </ItemsPanelTemplate>        </ItemsControl.ItemsPanel>        <ItemsControl.ItemContainerStyle>            <Style>                <Setter Property="Canvas.Left" Value="{Binding X}"/>                <Setter Property="Canvas.Top" Value="{Binding Y}"/>            </Style>        </ItemsControl.ItemContainerStyle>        <ItemsControl.ItemTemplate>            <DataTemplate>                <Border BorderBrush="Red" BorderThickness="1" Width="{Binding Width}" Height="{Binding Height}"/>            </DataTemplate>        </ItemsControl.ItemTemplate>    </ItemsControl></Grid>