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

Compares substrings of two specified String objects, ignoring or honoring their case, 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,
	bool ignoreCase
)

Parameters

strA
Type: System.String
The first string to use in the comparison.
indexA
Type: System.Int32
The position of the substring within strA.
strB
Type: System.String
The second string to use in the comparison.
indexB
Type: System.Int32
The position of the substring within strB.
length
Type: System.Int32
The maximum number of characters in the substrings to compare.
ignoreCase
Type: System.Boolean
true to ignore case during the comparison; otherwise, false.

Return Value

Type: System.Int32
A 32-bit signed integer that indicates the lexical relationship between the two comparands.

Value

Condition

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.

ExceptionCondition
ArgumentOutOfRangeException

indexA is greater than strA.Length.

-or-

indexB is greater than strB.Length.

-or-

indexA, indexB, or length is negative.

-or-

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.

Caution noteCaution

When comparing strings, you should call the Compare 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);
}


The path name needs to be compared in an invariant manner. 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);
}


The following example performs two comparisons of two substrings that only differ in case. The first comparison ignores case and the second comparison considers case.


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

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

    Console.WriteLine();
    Console.WriteLine("str1 = '{0}', str2 = '{1}'", str1, str2);
    Console.WriteLine("Ignore case:");
    result = String.Compare(str1, 2, str2, 2, 2, true);
    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(2, 2), str2);

    Console.WriteLine();
    Console.WriteLine("Honor case:");
    result = String.Compare(str1, 2, str2, 2, 2, false);
    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(2, 2), str2);
    }
}
/*
This example produces the following results:

str1 = 'MACHINE', str2 = 'machine'
Ignore case:
Substring 'CH' in 'MACHINE' is equal to substring 'ch' in 'machine'.

Honor case:
Substring 'CH' in 'MACHINE' is greater than substring 'ch' in 'machine'.
*/


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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