sample.cs

string sLastStoredWordText;

private void textControl1_KeyPress(object sender, KeyPressEventArgs e)
{
    // delimiter array 
    char[] cDelimiters = new char[] { ',','.','\r','\t',' ' };

    // check, if a delimiter has been pressed and if
    // misspelled words have been found
    if (!cDelimiters.Contains(e.KeyChar) ||
        textControl1.MisspelledWords == null ||
        textControl1.MisspelledWords.Count == 0)
        return;

    int iTextPosition = textControl1.InputPosition.TextPosition;

    // find a misspelled word at the input position
    MisspelledWord mwLastWord = 
        textControl1.MisspelledWords.GetItem(iTextPosition);

    // if the found word is not at the input position
    // store the last word and return
    if (mwLastWord.Start + mwLastWord.Length != iTextPosition + 1)
    {
        sLastStoredWordText = mwLastWord.Text; return;
    }

    // if the found word is the last word, store it and return
    // this prevents an auto replacement for intentionally wrong words
    if (mwLastWord.Text == sLastStoredWordText)
    {
        sLastStoredWordText = mwLastWord.Text; return;
    }

    // store the last word
    sLastStoredWordText = mwLastWord.Text;

    // create the suggestions, we only need the first
    txSpellChecker1.CreateSuggestions(mwLastWord.Text, 1);

    // if suggestions are found, replace the word with the suggestion
    if (txSpellChecker1.Suggestions.Count > 0)
    {
        e.Handled = true;

        string sSuggestion = txSpellChecker1.Suggestions[0].Text + " ";
        textControl1.MisspelledWords.Remove(mwLastWord, sSuggestion);
        textControl1.Select(mwLastWord.Start + sSuggestion.Length, 0);
    }
}