Add border around the whole Grid with multiple rows - wpf

Question

I'm trying to add a border around a Grid which currently contains 2 rows.
This grid is contained within a parent grid, which is a container for all the elements inside the window.
My code is the following:
<Grid> <!-- This is the parent grid which is holding everything-->
<TextBlock HorizontalAlignment="Center"
VerticalAlignment="Top"
Margin="0, 20, 0, 0"
FontSize="28"
>Welcome, User.</TextBlock>
<Grid x:Name="inner_grid" <!-- This is the grid I'm trying to enclose with a border-->
Width="400"
Height="250"
HorizontalAlignment="Left"
VerticalAlignment="Top"
Margin="20, 150, 0, 0"
>
<Grid.RowDefinitions>
<RowDefinition Height="auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBlock Grid.Row="0"
FontSize="22"
Margin="10, 0, 0, 0">Row number 1</TextBlock>
<TextBlock Grid.Row="1"
FontSize="22"
Margin="10, 0, 0, 0">Row number 2</TextBlock>
</Grid>
</Grid>
I've tried the other solutions, which mention the following construct:
<Border BorderBrush="Black" BorderThickness="2">
<Grid x:Name="inner_grid">
<!-- some code -->
</Grid>
</Border>
But what this did is, it put the border around the parent Grid, despite the Border tags enclosing the child Grid.
Another thing I tried is putting the <border> tag inside of the <Grid> itself, but that only put the border around the 0th row.
How exactly should I do this?
Edit (found the solution)
I've added a border around the child grid, but moved the Alignment and Margin attributes from the Grid into the Border.
Code is the following:
<!-- Move position attributes from the Grid into the enclosing Border -->
<Border BorderBrush="Black"
BorderThickness="2"
CornerRadius="10"
HorizontalAlignment="Left"
VerticalAlignment="Top"
Margin="20, 120, 0, 0">
<Grid x:Name="inner_grid"
Width="400"
Height="250">
<!-- Grid code here -->
</Grid>

Answer 1

You need to set VerticalAlignment and HorizontalAlignment of the border. If you omit it, the default value of Stretch is used. Stretch causes an element fill up all
the remaining space in the parent element. Possible values are Center, Left/Right, and Top/Bottom.
<Border BorderBrush="Black"
BorderThickness="2"
HorizontalAlignment="Center"
VerticalAlignment="Center">
<Grid x:Name="inner_grid">
<!-- some code -->
</Grid>
</Border>
Also keep in mind that the "Welcome, User." TextBlock and inner_grid inhabit the same cell in the outer grid. Thus they can visually overlap.

Answer 2

Welcome to SO.
I think the problem here is that your border is in fact around the inner control, but both your TextBlock and that child Grid are on the same row of the parent Grid. Try giving your parent Grid some RowDefinitions and specifying the Grid.Row for those child controls:
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition />
</Grid.RowDefinitions>
<!-- This is the parent grid which is holding everything-->
<TextBlock Grid.Row="0" HorizontalAlignment="Center"
VerticalAlignment="Top"
Margin="0, 20, 0, 0"
FontSize="28"
>Welcome, User.</TextBlock>
<Border Grid.Row="1" BorderBrush="Black" BorderThickness="2">
<Grid x:Name="inner_grid"
Width="400"
Height="250"
HorizontalAlignment="Left"
VerticalAlignment="Top"
Margin="20, 150, 0, 0"
>
<Grid.RowDefinitions>
<RowDefinition Height="auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBlock Grid.Row="0"
FontSize="22"
Margin="10, 0, 0, 0">Row number 1</TextBlock>
<TextBlock Grid.Row="1"
FontSize="22"
Margin="10, 0, 0, 0">Row number 2</TextBlock>
</Grid>
</Border>
</Grid>