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WPF Textbox Not Reacting to Validation Error

I have a WPF app with a UserControl that contains a Grid which in turn contains several TextBoxes:
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<TextBlock Grid.Column="0" Grid.Row="0"
Text="Application ID" />
<TextBox Grid.Column="1" Grid.Row="0"
Text="{Binding AzureAppID}"/>
<TextBlock Grid.Column="0" Grid.Row="1"
Text="Vault URL" />
<TextBox Grid.Column="1" Grid.Row="1"
Text="{Binding AzureVaultUrl}" />
</Grid>
I've implemented validation using the INotifyDataErrorInfo interface, which is working and correctly flags errors (e.g., AzureAppID, bound to the first TextBox, is not allowed to be empty).
In fact, if I enter an invalid value in either TextBox, the grid control which contains them lights up with a red border, signifying an error. But neither TextBox gets highlighted to indicate the error.
Why do other controls -- including other TextBoxes embedded within, say, a DataGrid -- react properly, but these ones inside a grid do not?
This is in a project built under Net 4.7.
Chalk This Up To Stupidity
It turns out my validation routine was tagging errors, in the case of the fields in question, with slightly different names from the properties the errors were associated with. Naturally, the WPF engine couldn't match up the error to the textboxes based on what the textboxes were bound to.

I think simple answer is that data grid is designed to listen notification ( say empty not allwoed would be notifified back with appropriate message via eventargs..ofcourse INotifyErrorInfo interface provides that infra behind-the-scene)
When considering plain grid/custom control as you say, you need to take care of that.

Apply MahApps.Metro theme and accent to other controls or rectangles

I'm trying to put a status bar on the bottom of my window that uses the same color scheme as the title bar. I know the piece I'm missing is style inheritance and/or template setting, but I've been reading for hours and I can't figure it out.
Here's how my window currently looks:
Here's how it looks in the designer:
What I want:
A status bar at the bottom of the window that mirrors the style of the titlebar. I recognize that my current implementation is probably less than great, so I'm also open to changing my statusbar defintiion as seen below. I tried to use an actual statusbar, but it wouldn't behave the way I wanted (the textboxes wouldn't fill the empty space, so the command line input textbox was very hard to click - maybe I was just doing something wrong). I'm assuming I can also apply the style to a rectangle just like anything else, right? I'm missing a critical component with the style property and probably the user of a template or a staticresource, but I'm totally lost.
Here's my current solution (a label and two textboxes for status updates and a cmdline):
<Grid Grid.Row="1">
<Grid.RowDefinitions>
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="0.5*"/>
<ColumnDefinition Width="0.5*"/>
</Grid.ColumnDefinitions>
<Label Grid.Column="0"/>
<Grid Grid.Column="1">
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<TextBox Grid.Row="0" Grid.Column="0"/>
<TextBox Grid.Row="0" Grid.Column="1"/>
</Grid>
</Grid>

I solved this by using the AccentColorBrush resource in my status bar grid.
<Grid Grid.Row="1" Background="{DynamicResource AccentColorBrush}">
I found it by inspecting many XAML files in MahApps.Metro on GitHub. This may seem obvious to some people, but for someone who is trying to learn XAML/WPF/MVVM, this wasn't straight forward. I hope this helps someone as I struggled with it for quite a while.

WPF clickable area around controls in grid

I have an issue with making a custom title bar for a form. It would contain a search textbox aswell as a few sliders, as seen on this image:
Now, imagine that as the title bar - everything that is not a part of the controls themselves (the textbox which is surrounded by a border element, and the slider) needs to be mousedownable for dragging purposes.
I've tried this:
<Grid MouseDown="TitleGridMouseDown">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="135"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="200"/>
</Grid.ColumnDefinitions>
<Slider Grid.Column="1" Margin="5 15 5 0" Width="100" MouseDown="TitleGridMouseDown"/>
<Slider Grid.Column="2" Margin="5 15 5 0"/>
<Border Grid.Column="3" CornerRadius="10" BorderThickness="1" BorderBrush="White" Width="180" Height="20" Background="White">
<TextBox Background="Transparent" BorderThickness="0" Height="20"/>
</Border>
</Grid>
However it's of no avail. There's a small part between the two sliders, like a few pixel area, which actually works (DragMove(); in the event itself). I don't have an awful lot of experience this type of things in WPF, but it feels to me like the area shrinks to the control. For instance, nothing changes if I place the border object into a button and try to bind the event to the button.
How should I approach this?

Your problem here is that you want to capture the MouseDown event on the grid element. Since your grid has no Background set, its defaulted to null. The MouseDown event does not get raised. Think of it like it is going through the grid without actually hitting it. A Background=Transparent on your top grid should solve the problem.

What's the best way to add an ui control in the grid at runtime?

t may be a basic question. But I can't figure it out after several hours research.
I have an item detail page. I want to add another grid in it whenever the scrollview reaches the right bottom. Right now I partially achieved this goal by adding a column in the xaml and toggle its visibility property.
<Grid x:Name="body" Style="{StaticResource LayoutRootStyle}">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Grid x:Name="dynamicGrid" Grid.Column="1" Grid.RowSpan="2" Visibility="Collapsed">
<Grid.RowDefinitions>
<RowDefinition Height="80"/>
<RowDefinition Height="360"/>
<RowDefinition Height="360"/>
</Grid.RowDefinitions>
<TextBlock .../>
<GridView .../>
<GridView .../>
</Grid>
And in code behind
if (//Reach the right side)
{
if (related.Visibility == Visibility.Collapsed)
{
related.Visibility = Windows.UI.Xaml.Visibility.Visible;
}
}
if (// Move away from right border)
{
related.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
}
It works to some point. But the animation is jumpy. Sometime, the scrollviewer even refuse to go back to the beginning. I guess the problem is when I adding/removing ui control at runtime, the scrollviewer doesn't handle it quite well.
I'm wondering is there a better way to achieve this feature? Any suggestion is welcomed.

You can add a child control in a grid by calling grid.Children.Add(newChildControl). You can also assign the child control to specific row/column/span by calling Grid.SetRow/Column/RowSpan/ColumnSpan.

Handling Different Font Sizes Due To Display Properties in a WPF App?

My group is building an editor-type app in WPF. One thing we noticed is that on my WinXP machine, running with the "windows classic style" theme, the text on buttons is fits fine. However on my friend's machine, who's running with the "windows xp style" theme, the font size is bigger so text on buttons get clipped at the bottom.
Is there a way to handle this nicely, like automatically resizing controls to fit the text?
I hesitate to manually resize the button to fit his layout as anyone else can have totally different settings through the Display Properties and Accessibility Options.
Thanks!

A WPF button will automatically resize to fit the content that it has been given, however it will only do this when it is inside a container that does not enforce size and its size has not been set manually. To prove this mess around with the font size in the following code snippet:
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Button
Grid.Column="1"
Grid.Row="1"
FontSize="24"
Content="QWERTY"/>
</Grid>
I guess that your buttons haven't resized because you have constrained them. To fix this you need to decide how you want them to resize (which can be very complicated when elements would overlap if they just grew blindly) and if none of the supplied panel types perform the growth behaviour that you are looking for then you may need to write your own that does.

Have you hardcoded element sizes using Width and Height properties? In WPF the recommended way to do this is to use the several layout containers.
The following is an example of a grid which lays two buttons at the bottom and a textbox at the top.
<Grid>
<Grid.RowDefinitions>
<!-- TextBox row with unspecified height. -->
<RowDefinition Height="*"/>
<!-- Button row with automated height so it resizes to
fit the content -->
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<!-- Textbox on first row. -->
<TextBox Margin="3" Name="textBox1" Grid.Row="0" AcceptsReturn="True" />
<!-- StackPanel which lays the two buttons at the bottom horizontally.
RightToLeft is specified so that the first button appears on right.
-->
<StackPanel Grid.Row="1" HorizontalAlignment="Right"
Orientation="Horizontal" FlowDirection="RightToLeft">
<!-- The buttons. Only padding and margin are hardcoded so these
can resize to the contents -->
<Button Padding="3" Margin="3">OK</Button>
<Button Padding="3" Margin="3">Cancel</Button>
</StackPanel>
</Grid>