String comparison in .Net: “+” vs “-”

Question

I always assumed that .Net compares strings lexicographically, according to the current culture. But there is something strange when one of the strings ends on '-':

"+".CompareTo("-")
Returns: 1

"+1".CompareTo("-1")
Returns: -1

I get it an all cultures I tried, including the invariant one. Can anyone explain what is going on, and how can I get the consistent character-by-character ordering for the current locale?

Answer 1

There isn't necessarily a consistent character-by-character ordering for any particular locale.

From the MSDN documentation:

For example, a culture could specify that certain combinations of characters be treated as a single character, or uppercase and lowercase characters be compared in a particular way, or that the sorting order of a character depends on the characters that precede or follow it.

The only way to ensure consistent character-by-character ordering is by using an ordinal comparison, as demonstrated in Anton's answer.

Answer 2

Try changing this to

string.Compare("+", "-", StringComparison.Ordinal); // == -2
string.Compare("+1", "-1", StringComparison.Ordinal); // == -2

Answer 3

        string.Compare("+", "-");
        string.Compare("+", "-", StringComparison.CurrentCulture);
        string.Compare("+", "-", StringComparison.InvariantCulture);
        string.Compare("+", "-", StringComparison.InvariantCultureIgnoreCase);

        // All Pass

the two value are equal because, inguisitic casing is being taken into consideration

FIX:

replace the invariant comparison with an ordinal comparison.This means the decisions are based on simple byte comparisons and ignore casing or equivalence tables that are parameterized by culture.

reference : Use ordinal StringComparison

string.Compare("+", "-", StringComparison.Ordinal); // fail

Answer 4

You'll probably want to use the true minus sign, Unicode codepoint \u2212. The minus sign you use in programming (\u002d) is a "hyphen-minus", its collation order is context sensitive because it is also frequently used as a hyphen. There's more than you'll want to know about the many different kind of dashes in this article.

Answer 5

use CompareOrdinal. e.g

String.CompareOrdinal("+1","-1");
-2
String.CompareOrdinal("+","-");
-2