Toolbox and Designer
In a WPF application, you declare the spell checker of TX Spell .NET as a resource of the window in XAML and connect the TextControl to it by its key. When the spell checker can't be found in the toolbox, isn't known in XAML, or spell checking doesn't start, the cause is usually this declaration or the connection. Visual Studio Toolbox and Designer describes the design-time support.
The Spell Checker Isn't in the Toolbox
After installing TXTextControl.TXSpell.WPF.SDK, the toolbox has no entry for the spell checker.
The WPF spell checker, TXSpellChecker, has no toolbox item: you map the namespace of TX Spell .NET to a prefix in the Window element and declare the spell checker in the resources of the window, as Connect the Spell Checker in XAML shows. Then build the project.
Spell Checking Doesn't Start
The spell checker is declared, but misspelled words in the TextControl aren't marked.
The TextControl must be connected to the spell checker by the key of the resource, and spell checking must be switched on. Check that the SpellChecker property of the TextControl holds the key as plain text, such as txSpellChecker1, that IsSpellCheckingEnabled is True, and that each prefix in the XAML, the one of TX Text Control as well as spell, is declared in the Window element. Connect the Spell Checker in XAML shows the complete markup. If the words are still not marked, the language data may be missing; see Dictionaries Not Found.
The XAML Designer Asks to Restart
When you add the first control of TX Text Control from the toolbox, the XAML Designer asks to be restarted. This concerns the controls of TX Text Control, not TX Spell .NET: click OK and build the solution, as No Toolbox Item shows.