vb.net fastest way to match two long list and get which word is not found

vb.net fastest way to match two long list and get which word is not found

i have "dictionary.txt" file in which it contains all dictionary words i
am trying to syntax highlighting in richtextbox (vb.net) of misspelled
word
is there any way to check misspelled words in richtextbox by using
dictionary.txt file
i am using for loop and checking each word but its taking too much time
Dim p As Integer = 0
For i = 0 To aryTextFile.Length - 1
aryTextFile(i) = aryTextFile(i).Replace(",", "").Replace(".", "")
If wordslistD.Contains(LCase(aryTextFile(i))) Then
Else
MisSpelledList.Add(aryTextFile(i))
End If
ProgressBar1.Value = p
p = p + 1
Next