Character after hyphen affects string.compare

Question

I would expect "2-" and "22" to always compare the same way, but changing the 3rd character changes the sort order.

string.Compare("2-1","22-", StringComparison.CurrentCulture) //-1
string.Compare("2-2","22-", StringComparison.CurrentCulture) //1

What on earth is happening here?

Our culture is en-US by the way.

Answer 1

As per the documentation:

Character sets include ignorable characters. The Compare(String, String, StringComparison) method does not consider such characters when it performs a culture-sensitive comparison. To recognize ignorable characters in your comparison, supply a value of StringComparison.Ordinal or OrdinalIgnoreCase for the comparisonType parameter.

In your case, the hyphen is an ignorable character. In this case it means that the middle hyphen isn't taken into account. That means it actually compares 21 and 22 to 22-, which will evaluate to -1 and 1 respectively.