#949 – Add a Custom Dictionary for Spell Checking in a TextBox

The built-in spell checker in a TextBox uses a predefined dictionary to look up words.  This means that there may be words flagged as misspelled because they are not in the dictionary.

You can add a custom dictionary to WPF’s spell checker by creating a lexicon (.lex) file.  To create a custom dictionary, start by creating a .lex file in your project.

Add any custom words to your dictionary, one line at a time.

Set the Build Action of the .lex file to Resource.

In the .xaml file containing the TextBox element, define a namespace that refers to the system assembly.

        xmlns:sys="clr-namespace:System;assembly=system"

And set the SpellCheck.CustomDictionaries element using a Uri to refer to your dictionary.

        <TextBox Name="txtMyText" Margin="5" Height="100"
                 TextWrapping="Wrap"
                 VerticalScrollBarVisibility="Auto"
                 SpellCheck.IsEnabled="True">
            <SpellCheck.CustomDictionaries>
                <sys:Uri>pack://application:,,,/MyDictionary.lex</sys:Uri>
            </SpellCheck.CustomDictionaries>
        </TextBox>

The spell checker now recognizes your custom words.