Cannot see _ (underscore) in WPF content - wpf

Question

A very simple question:
Why I cant see _ (underscore) in WPF content?
For instance the content of
<Label Content="test_t" Name="label2" />
is shown as "testt" (with the underscore not shown).

Answer 1

Labels support mnemonics (i.e. you can use ctrl+(key) to give them focus). You define the mnemonic key using an underscore.
http://www.charlespetzold.com/blog/2006/01/061004.html
If you want to see underscores, replace single underscores with double underscores.

Answer 2

This is because Label supports defining a mnemonic based on its content, which is done by prefixing the mnemonic with an underscore (the same thing that happens in Windows Forms with &).
Use a double underscore if you want a literal one to appear:
<Label Content="test__t" Name="label2" />

Answer 3

I know im late to the party but I believe that if you don't have the Label associated to a TextBox than you should use a TextBlock instead.
Changing your control to a TextBlock solves this issue since only Label has the mnemonic support

Answer 4

This style solves your problem:
<Style x:Key="{x:Type Label}"
TargetType="{x:Type Label}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Label}">
<Border Background="{TemplateBinding Background}"
BorderThickness="{TemplateBinding BorderThickness}"
BorderBrush="{TemplateBinding BorderBrush}"
Padding="{TemplateBinding Padding}"
SnapsToDevicePixels="true">
<ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
RecognizesAccessKey="False"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsEnabled"
Value="false">
<Setter Property="Foreground"
Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>

Answer 5

I was binding to a data source which I didn't want to change, so I used a custom converter to create the missing underscore:
[ValueConversion(typeof(string), typeof(string))]
public class ShowUnderscoreConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture) =>
value is string text ? text.Replace("_", "__") : null;
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) =>
value is string text ? text.Replace("__", "_") : null;
}