String.Compare Method (String, String, Boolean)
Compares two specified String objects, ignoring or honoring their case, and returns an integer that indicates their relative position in the sort order.
Assembly: mscorlib (in mscorlib.dll)
- Type: System.String
The first string to compare.
- Type: System.String
The second string to compare.
- Type: System.Boolean
true to ignore case during the comparison; otherwise, false.
Return ValueType: System.Int32
A 32-bit signed integer that indicates the lexical relationship between the two comparands.
Less than zero
strA is less than strB.
strA equals strB.
Greater than zero
strA is greater than strB.
The comparison uses the current culture to obtain culture-specific information such as casing rules and the alphabetic order of individual characters. 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 comparison is performed using word sort rules. For more information about word, string, and ordinal sorts, see System.Globalization.CompareOptions.
When comparing strings, you should call the Compare(String, String, StringComparison) method, which requires that you explicitly specify the type of string comparison that the method uses. For more information, see Best Practices for Using Strings in the .NET Framework.
One or both comparands can be a null reference (Nothing in Visual Basic). By definition, any string, including the empty string (""), compares greater than a null reference; and two null references compare equal to each other.
The comparison terminates when an inequality is discovered or both strings have been compared. However, if the two strings compare equal to the end of one string, and the other string has characters remaining, then the string with remaining characters is considered greater. The return value is the result of the last comparison performed.
Unexpected results can occur when comparisons are affected by culture-specific casing rules. For example, in Turkish, the following example yields the wrong results because the file system in Turkish does not use linguistic casing rules for the letter "i" in "file".
Compare the path name to "file" using an ordinal comparison. The correct code to do this is as follows:Notes to Callers
Character sets include ignorable characters. The method does not consider such characters when it performs a culture-sensitive comparison. For example, a culture-sensitive, case-insensitive comparison of "animal" with "Ani-mal" (using a soft hyphen, or U+00AD) indicates that the two strings are equivalent, as the following example shows.
To recognize ignorable characters in a string comparison, call the Compare method and supply a value of either CompareOptions.Ordinal or CompareOptions.OrdinalIgnoreCase for the comparisonType parameter.