KeyPhrase count is always one

[endintiers]

Because count++ happens AFTER the count is updated.
The bit of code that counts how many time we have seen a keyphrase should be:
int count;
if (keyPhrases.TryGetValue(keyPhrase.ToLower(), out count))
{
count++;
keyPhrases[keyPhrase.ToLower()] = count;
}
That will make the sample MUCH better.