System.String.Compare Method

Compares substrings of two specified string objects and returns an integer that indicates their relative position in the sort order.

Syntax

public static int Compare (string strA, int indexA, string strB, int indexB, int length)

Parameters

strA
The first string to use in the comparison.
indexA
The position of the substring within strA.
strB
The second string to use in the comparison.
indexB
The position of the substring within strB.
length
The maximum number of characters in the substrings to compare.

Returns

A 32-bit signed integer indicating the lexical relationship between the two comparands.

Less than zero

The substring in strA is less than the substring in strB.

Zero

The substrings are equal, or length is zero.

Greater than zero

The substring in strA is greater than the substring in strB.

Exceptions

TypeReason
ArgumentOutOfRangeException

The sum of indexA and length is greater than strA .Length .

-or-

The sum of indexB and length is greater than strB .Length .

-or-

indexA, indexB, or length is negative.

Remarks

The substrings to compare start in strA at indexA and in strB at indexB. Both indexA and indexB are zero-based; that is, the first character in strA and strB is at position zero. The length of the first substring is equal to the length of strA minus indexA plus one. The length of the second substring is equal to the length of strB minus indexB plus one.

The number of characters to compare is the lesser of the lengths of the two substrings, and length. The indexA, indexB, and length parameters must be nonnegative.

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.

Note:

When comparing strings, you should call the string.Compare(string, int, string, int, int, 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 null. 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 substrings 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".

code reference: System.String.Compare#2

Compare the path name to "file" using an ordinal comparison. The correct code to do this is as follows:

code reference: System.String.Compare#3

Example

The following example demonstrates comparing substrings.

C# Example

using System;
public class StringCompareExample {
 public static void Main() {
 string strA = "A string";
 string strB = "B ring";
 int first = String.Compare( strA, 4, strB, 2, 3 );
 int second = String.Compare( strA, 3, strB, 3, 3 );
 Console.WriteLine( "When the substring 'rin' of 'A string' is compared to the substring 'rin' of 'B ring', the return value is {0}.", first );
 Console.WriteLine( "When the substring 'tri' of 'A string' is compared to the substring 'ing' of 'B ring', the return value is {0}.", second );
 }
}
   

The output is

When the substring 'rin' of 'A string' is compared to the substring 'rin' of 'B ring', the return value is 0.
When the substring 'tri' of 'A string' is compared to the substring 'ing' of 'B ring', the return value is 1.

Requirements

Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0