First, you need to add "NHunspell" from "NuGet" and import it. The specific operation is as follows：

Right click the Reference and select "Manage NuGet Packages...",

 

then type "NHunspell " in the search bar and install it:

 

Second step, you need to create a folder to store ".aff" and ".dic" like this.

 

Download the "zip" containing the corresponding file, you can access

The last step, you can refer to the following code:

Private Sub btCheck_Click(sender As Object, e As EventArgs) Handles btCheck.Click        Dim affFile As String = AppDomain.CurrentDomain.BaseDirectory & "../../Dictionaries/en_us.aff"        Dim dicFile As String = AppDomain.CurrentDomain.BaseDirectory & "../../Dictionaries/en_us.dic"        lbSuggestion.Items.Clear()        lbmorph.Items.Clear()        lbStem.Items.Clear()        Using hunspell As New Hunspell(affFile, dicFile)            Dim correct As Boolean = hunspell.Spell(TextBox1.Text)            checklabel.Text = TextBox1.Text + " is spelled " & (If(correct, "correct", "not correct"))            Dim suggestions As List(Of String) = hunspell.Suggest(TextBox1.Text)            countlabel.Text = "There are " & suggestions.Count.ToString() & " suggestions"            For Each suggestion As String In suggestions                lbSuggestion.Items.Add("Suggestion is: " & suggestion)            Next            Dim morphs As List(Of String) = hunspell.Analyze(TextBox1.Text)            For Each morph As String In morphs                lbmorph.Items.Add("Morph is: " & morph)            Next            Dim stems As List(Of String) = hunspell.Stem(TextBox1.Text)            For Each stem As String In stems                lbStem.Items.Add("Word Stem is: " & stem)            Next        End Using    End Sub

Result:

 

Refer to: 

Besides, the control "TextBox" and "RichTextBox" in WPF can also implements spell checking via displaying wavy lines. For more details, you can refer to .