How to get WPF Window to autosize to content and n

I have a dialog containing 2 TextBlocks, a Progress Bar and a cancel Button.

Here is the XAML:

Window x:Class="WpfApplication4.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:WpfApplication4"
    mc:Ignorable="d"
    Title="MainWindow" Height="Auto" Width="200">
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>
    </Grid.RowDefinitions>

    <TextBlock x:Name="txtFirst" Grid.Row="0"  Margin="5" TextWrapping="Wrap">This is a really really really really long string that wraps</TextBlock>
    <TextBlock x:Name="txtSecond" Grid.Row="1"  Margin="5" Text="A Shorter string" TextWrapping="Wrap" MaxWidth="200"/>
    <ProgressBar x:Name="prgProgress" Grid.Row="2" Margin="5" Height="20" />
    <Button x:Name="btnCancel" Grid.Row="3" Margin="5" Height="25" Width="50"/>
</Grid>

I would like the Window not to have a fixed height but auto adjust its height based on the size of its children and no more, but can’t see a way to do this. At the moment when I don’t assign anything to the Window’s height, it seems to adopt a height that is much bigger that the content Not sure why, or where it gets height value from? If I set Windows Height = “Auto” I get the same thing. All the heights for the RowDefinitions are set to “Auto”, which I take to mean ‘set row height to be row child height’.

Many thanks in advance for any help.

You need to use SizeToContent property, check the msdn link below.

https://msdn.microsoft.com/en-us/library/system.windows.window.sizetocontent(v=vs.110).aspx