WPF UserControl fill mainwindow

Question

I am having trouble getting my UserControl to properly fill/resize with the parent window. I'm writing a WPF application using MVVM. I've searched for other answers, and I haven't been able to figure this out.

MainWindow.xaml

<Window x:Class="QiXR.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:vm="clr-namespace:QiXR.ViewModel"
    xmlns:vw="clr-namespace:QiXR.View"
    Title="MainWindow">
<Window.Resources>
    <DataTemplate DataType="{x:Type vm:XRTestCaseListViewModel}">
        <vw:XRTestCaseListView/>
    </DataTemplate>

</Window.Resources>
<Grid>
    <ItemsControl ItemsSource="{Binding ViewModels}" />
</Grid>

UserControl

<UserControl x:Class="QiXR.View.XRTestCaseListView"
         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"
         VerticalAlignment="Stretch" HorizontalAlignment="Stretch" HorizontalContentAlignment="Stretch" VerticalContentAlignment="Stretch">
<UserControl.Resources>
    <Style x:Key="DataGridCheckBoxStyle" TargetType="CheckBox" BasedOn="{StaticResource {x:Type CheckBox}}">
        <Setter Property="VerticalAlignment" Value="Center"/>
        <Setter Property="HorizontalAlignment" Value="Center"/>
    </Style>
</UserControl.Resources>

<Grid VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="160"/>
        <ColumnDefinition Width="160"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
        <RowDefinition Height="30"/>
        <RowDefinition Height="*"/>
        <RowDefinition Height="45"/>
    </Grid.RowDefinitions>

Here's what the display looks like when I launch it UserControl in MainWindow

Is it possible to do this in the xaml of either the UserControl or MainWindow? Thanks

Answer 1

An ItemsControl defaults to using a StackPanel to display data, and StackPanel limits its size to the size of its children.

Try switching the ItemsPanelTemplate to something like a DockPanel instead if you only have one item in your ViewModels collection :

<ItemsControl ItemsSource="{Binding ViewModels}">
    <!-- ItemsPanelTemplate -->
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <DockPanel />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
</ItemsControl>

You'll also have to set the ItemContainerStyle property for DockPanel.Dock="Top" if you plan on having more than one item, perhaps with a converter so the last item is DockPanel.Dock="Fill". Or switch to use a different panel type that also stretches to fill all available space, and allows it's children to stretch as well.

That said, I'd recommend switching to using a ContentControl instead of an ItemsControl if you are only displaying one item.

<ContentControl Content="{Binding MyViewModel}" />