Create a Control Template
Create a copy of the default ControlTemplate for CheckBox:
Solution Explorer > Dependencies > Packages > Microsoft.WindowsAppSDK …
This package contains the WinUI library and a generic.xaml file that contains all the styles for the controls of WinUI.
… Right-click Microsoft.WindowsAppSDK > Open file in Explorer > lib > net6.0-windows.10.x.y.z > Microsoft.WinUI > Themes > generic.xaml
generic.xaml
Resources/Styles.xaml
Paste the style for the CheckBox copied from generic.xaml:
Resources/Styles.xaml
The CheckBox is actually a Grid:
The VisualStateGroups define the UI of the CheckBox based on its state. For example, if the CheckBox is unchecked, then UncheckedNormal is active:
The CheckBox (Grid) contains two column defintions:
The first ColumnDefinition has a Rectangle and a FontIcon which is actually the checkmark (defined in its Glyph property):
This ContentPresenter displays the Content of the CheckBox:
To change the checkmark, go to the FontIcon > right-click SymbolThemeFontFamily > Go to definition:
This takes you to generic.xaml
Searching for these fonts takes you to
Microsoft Docs with other icons and descriptions. The one we want is the X which has a Unicode point of e711.
Styles.xaml
Change the Glyph, which currently uses Unicode point E001 to E711:
