Why the height is incorrect? - wpf

Question

I have a simple WPF form with next XAML
<Window x:Class="ReikartzDataConverter.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="650" Width="800">
<Grid Width="780" Height="650">
<Grid.RowDefinitions>
<RowDefinition Height="50"></RowDefinition>
<RowDefinition Height="500"></RowDefinition>
<RowDefinition Height="50"></RowDefinition>
<RowDefinition Height="50"></RowDefinition>
</Grid.RowDefinitions>
<Label Grid.Row="0" Content="Process information" Height="28" HorizontalAlignment="Left" Margin="0,20,0,0" Name="label1" VerticalAlignment="Top" Width="235" />
<DataGrid Grid.Row="1" Width="780" Height="500" Name="paysTable">
</DataGrid>
<Label Grid.Row="2" Height="28" Name="lblError" VerticalAlignment="Top" Visibility="Hidden" Foreground="OrangeRed" FontWeight="Bold" FontSize="12" />
<Button Grid.Row="3" Content="Quit" Height="23" Name="button1" VerticalAlignment="Top" Width="75" Click="button1_Click" />
<Button Grid.Row="3" Content="Start" Height="23" Name="button2" VerticalAlignment="Top" Width="75" Click="button2_Click" />
</Grid>
</Window>
Why my 2 buttons from Grid.Row="3" are partially located out of the visible part of the window?
My window has the height="650" and my Grid also has the Height="650"
I have 4 Rows: 50, 50, 500, 50. So the last row must be located inside the window. Why is not so?

Answer 1

The Window Height of 650 also includes the 'chrome', i.e. the bar at the top of the window with the minimize, maximize buttons. It is a much better approach to create a layout which does not rely on a specific height. In your case, I would make the row that contains your grid auto-sized:
<Grid.RowDefinitions>
<RowDefinition Height="50"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="50"></RowDefinition>
<RowDefinition Height="50"></RowDefinition>
</Grid.RowDefinitions>
Then you can remove the height / width from your Grid, and all your other UI elements, just let the grid dictate the size of its children.

Answer 2

#ColinE's answer is the right approach in that you should adopt a "fluid" layout in WPF, but if you really want a fixed height for your content and you need the window to be the right size, you can use the SizeToContent property:
<Window x:Class="ReikartzDataConverter.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Width="800"
SizeToContent="Height">
<Grid Width="780" Height="650">
...
</Grid>
</Window>
Setting SizeToContent to "Height" will make the window resize vertically so that its contents fit. Don't forget to remove the Height property from the Window declaration.