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String.Equals Method (String, StringComparison)

Determines whether this string and a specified String object have the same value. A parameter specifies the culture, case, and sort rules used in the comparison.

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

public bool Equals (
	string value,
	StringComparison comparisonType
)
public boolean Equals (
	String value, 
	StringComparison comparisonType
)
public function Equals (
	value : String, 
	comparisonType : StringComparison
) : boolean
Not applicable.

Parameters

value

A String object.

comparisonType

One of the System.StringComparison values.

Return Value

true if the value of the value parameter is the same as this string; otherwise, false.

Exception typeCondition

NullReferenceException

This string is a null reference (Nothing in Visual Basic).

ArgumentException

comparisonType is not a StringComparison value.

The comparisonType parameter indicates whether the comparison should use the current or invariant culture, honor or ignore the case of the two strings being compared, or use word or ordinal sort rules.

The following code example uses three versions of the Equals method to determine whether a String object and a StringBuilder object are equal. The results are affected by the choice of culture, whether case is ignored, and whether an ordinal comparison is performed.

// This example demonstrates the 
// System.String.Equals(String, StringComparison) method.

using System;
using System.Threading;

class Sample 
{
    public static void Main() 
    {
    string intro = "Compare three versions of the letter I using different " + 
                   "values of StringComparison.";

// Define an array of strings where each element contains a version of the 
// letter I. (An array of strings is used so you can easily modify this 
// code example to test additional or different combinations of strings.)  

    string[] threeIs = new string[3];
// LATIN SMALL LETTER I (U+0069)
    threeIs[0] = "\u0069";
// LATIN SMALL LETTER DOTLESS I (U+0131)
    threeIs[1] = "\u0131";
// LATIN CAPITAL LETTER I (U+0049)
    threeIs[2] = "\u0049";

    string[] unicodeNames = 
             {
             "LATIN SMALL LETTER I (U+0069)", 
             "LATIN SMALL LETTER DOTLESS I (U+0131)", 
             "LATIN CAPITAL LETTER I (U+0049)"
             };

    StringComparison[] scValues = {
        StringComparison.CurrentCulture,
        StringComparison.CurrentCultureIgnoreCase,
        StringComparison.InvariantCulture,
        StringComparison.InvariantCultureIgnoreCase,
        StringComparison.Ordinal,
        StringComparison.OrdinalIgnoreCase };

//
    Console.Clear();
    Console.WriteLine(intro);

// Display the current culture because the culture-specific comparisons
// can produce different results with different cultures.
    Console.WriteLine("The current culture is {0}.\n", 
                       Thread.CurrentThread.CurrentCulture.Name);

// Determine whether three versions of the letter I are equal to each other. 
    foreach (StringComparison sc in scValues)
        {
        Console.WriteLine("StringComparison.{0}:", sc);

// LATIN SMALL LETTER I (U+0069) : LATIN SMALL LETTER DOTLESS I (U+0131)
        Test(0, 1, sc, threeIs, unicodeNames);

// LATIN SMALL LETTER I (U+0069) : LATIN CAPITAL LETTER I (U+0049)
        Test(0, 2, sc, threeIs, unicodeNames);

// LATIN SMALL LETTER DOTLESS I (U+0131) : LATIN CAPITAL LETTER I (U+0049)
        Test(1, 2, sc, threeIs, unicodeNames);

        Console.WriteLine();
        }
    }

    protected static void Test(int x, int y, 
                               StringComparison comparison, 
                               string[] testI, string[] testNames)
    {
    string resultFmt = "{0} is {1}equal to {2}";
    string result = "not ";
//
    if (testI[x].Equals(testI[y], comparison)) 
        result = "";
    Console.WriteLine(resultFmt, testNames[x], result, testNames[y]);
    }
}

/*
This code example produces the following results:

Compare three versions of the letter I using different values of StringComparison.
The current culture is en-US.

StringComparison.CurrentCulture:
LATIN SMALL LETTER I (U+0069) is not equal to LATIN SMALL LETTER DOTLESS I (U+0131)
LATIN SMALL LETTER I (U+0069) is not equal to LATIN CAPITAL LETTER I (U+0049)
LATIN SMALL LETTER DOTLESS I (U+0131) is not equal to LATIN CAPITAL LETTER I (U+0049)

StringComparison.CurrentCultureIgnoreCase:
LATIN SMALL LETTER I (U+0069) is not equal to LATIN SMALL LETTER DOTLESS I (U+0131)
LATIN SMALL LETTER I (U+0069) is equal to LATIN CAPITAL LETTER I (U+0049)
LATIN SMALL LETTER DOTLESS I (U+0131) is not equal to LATIN CAPITAL LETTER I (U+0049)

StringComparison.InvariantCulture:
LATIN SMALL LETTER I (U+0069) is not equal to LATIN SMALL LETTER DOTLESS I (U+0131)
LATIN SMALL LETTER I (U+0069) is not equal to LATIN CAPITAL LETTER I (U+0049)
LATIN SMALL LETTER DOTLESS I (U+0131) is not equal to LATIN CAPITAL LETTER I (U+0049)

StringComparison.InvariantCultureIgnoreCase:
LATIN SMALL LETTER I (U+0069) is not equal to LATIN SMALL LETTER DOTLESS I (U+0131)
LATIN SMALL LETTER I (U+0069) is equal to LATIN CAPITAL LETTER I (U+0049)
LATIN SMALL LETTER DOTLESS I (U+0131) is not equal to LATIN CAPITAL LETTER I (U+0049)

StringComparison.Ordinal:
LATIN SMALL LETTER I (U+0069) is not equal to LATIN SMALL LETTER DOTLESS I (U+0131)
LATIN SMALL LETTER I (U+0069) is not equal to LATIN CAPITAL LETTER I (U+0049)
LATIN SMALL LETTER DOTLESS I (U+0131) is not equal to LATIN CAPITAL LETTER I (U+0049)

StringComparison.OrdinalIgnoreCase:
LATIN SMALL LETTER I (U+0069) is not equal to LATIN SMALL LETTER DOTLESS I (U+0131)
LATIN SMALL LETTER I (U+0069) is equal to LATIN CAPITAL LETTER I (U+0049)
LATIN SMALL LETTER DOTLESS I (U+0131) is not equal to LATIN CAPITAL LETTER I (U+0049)

*/

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

.NET Compact Framework

Supported in: 2.0

XNA Framework

Supported in: 1.0

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