stop words removal and rooting

Question

I have thousands of files, I need to remove all stop words, and get each words' Root. I have this code, but it is very slow, how to speed up my code to get this on the fly? thanks

for (int i = 0; i < Terms.Count(); i++)

{

Terms[i] = RemovePuctuations(Terms[i]);

Terms[i] = RemoveDiacrities(Terms[i]);

if (!IsArabicWord(Terms[i]))

{

Terms[i] = " ";

continue;

}

stemmer.initComponents();

Terms[i] = stemmer.stemWord(Terms[i]);

if (StopWordsBLL.StopWords.Contains(Terms[i]))

Terms[i] = " ";

}