Compare Method (String, Int32, String, Int32, Int32)

String.Compare Method (String, Int32, String, Int32, Int32)


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

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)

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


Type: System.String

The first string to use in the comparison.

Type: System.Int32

The position of the substring within strA.

Type: System.String

The second string to use in the comparison.

Type: System.Int32

The position of the substring within strB.

Type: System.Int32

The maximum number of characters in the substrings to compare.

Return Value

Type: System.Int32

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



Less than zero

The substring in strAprecedes the substring in strB in the sort order.


The substrings occur in the same position in the sort order, or length is zero.

Greater than zero

The substring in strAfollows the substring in strB in the sort order.

Exception Condition

indexA is greater than strA.Length.


indexB is greater than strB.Length.


indexA, indexB, or length is negative.


Either indexA or indexB is null, and length is greater than zero.

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.


When comparing strings, you should call the Compare(String, Int32, String, Int32, Int32, 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".

static bool IsFileURI(String path)
    return (String.Compare(path, 0, "file:", 0, 5, true) == 0);

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

static bool IsFileURI(String path)
    return (String.Compare(path, 0, "file:", 0, 5, StringComparison.OrdinalIgnoreCase) == 0);

Notes to Callers:

Character sets include ignorable characters. The Compare(String, Int32, String, Int32, Int32) method does not consider these characters when it performs a linguistic or culture-sensitive comparison. To recognize ignorable characters in your comparison, call theCompare(String, Int32, String, Int32, Int32, StringComparison) method and supply a value of CompareOptions.Ordinal or CompareOptions.OrdinalIgnoreCase for the comparisonType parameter.

The following example compares two substrings.

// Sample for String.Compare(String, Int32, String, Int32, Int32)
using System;

class Sample {
    public static void Main() {
//                 0123456
    String str1 = "machine";
    String str2 = "device";
    String str;
    int result;

    Console.WriteLine("str1 = '{0}', str2 = '{1}'", str1, str2);
    result = String.Compare(str1, 2, str2, 0, 2);
    str = ((result < 0) ? "less than" : ((result > 0) ? "greater than" : "equal to"));
    Console.Write("Substring '{0}' in '{1}' is ", str1.Substring(2, 2), str1);
    Console.Write("{0} ", str);
    Console.WriteLine("substring '{0}' in '{1}'.", str2.Substring(0, 2), str2);
This example produces the following results:

str1 = 'machine', str2 = 'device'
Substring 'ch' in 'machine' is less than substring 'de' in 'device'.

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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