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String.Compare Method (String, String, Boolean)

.NET Framework 1.1

Compares two specified String objects, ignoring or honoring their case.

[Visual Basic]
Overloads Public Shared Function Compare( _
   ByVal strA As String, _
   ByVal strB As String, _
   ByVal ignoreCase As Boolean _
) As Integer
[C#]
public static int Compare(
 string strA,
 string strB,
 bool ignoreCase
);
[C++]
public: static int Compare(
 String* strA,
 String* strB,
 bool ignoreCase
);
[JScript]
public static function Compare(
   strA : String,
 strB : String,
 ignoreCase : Boolean
) : int;

Parameters

strA
The first String.
strB
The second String.
ignoreCase
A Boolean indicating a case-sensitive or insensitive comparison. (true indicates a case-insensitive comparison.)

Return Value

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

Value Meaning
Less than zero strA is less than strB.
Zero strA equals strB.
Greater than zero strA is greater than strB.

Remarks

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.

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 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 String 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 String IsFileURI(String path) { 
   return (String.Compare(path, 0, "file:", 0, 5, true, CultureInfo.InvariantCulture)== 0); }

Example

[C#, C++] The following code example demonstrates how this Compare method is equivalent to using ToUpper or ToLower when comparing strings.

[C#] 
unsafe
{
    // Null terminated ASCII characters in an sbyte array
    String szAsciiUpper = null;
    sbyte[] sbArr1 = new sbyte[] { 0x41, 0x42, 0x43, 0x00 };
    // Instruct the Garbage Collector not to move the memory
    fixed(sbyte* pAsciiUpper = sbArr1)
    {
        szAsciiUpper = new String(pAsciiUpper);
    }
    String szAsciiLower = null;
    sbyte[] sbArr2 = { 0x61, 0x62, 0x63, 0x00 };
    // Instruct the Garbage Collector not to move the memory
    fixed(sbyte* pAsciiLower = sbArr2)
    {
        szAsciiLower = new String(pAsciiLower, 0, sbArr2.Length);
    }
    // Prints "ABC abc"
    Console.WriteLine(szAsciiUpper + " " + szAsciiLower);

    // Compare Strings - the result is true
    Console.WriteLine("The Strings are equal when capitalized ? " +
        (String.Compare(szAsciiUpper.ToUpper(), szAsciiLower.ToUpper())==0?"true":"false") );

    // This is the effective equivalent of another Compare method, which ignores case
    Console.WriteLine("The Strings are equal when capitalized ? " +
        (String.Compare(szAsciiUpper, szAsciiLower, true)==0?"true":"false") );
}

[C++] 
// Null terminated ASCII characters in a simple char array
char charArray3 [4]  = { 0x41, 0x42, 0x43, 0x00 };
char* pstr3 = &charArray3[0];
String* szAsciiUpper = new String(pstr3);

char charArray4 [4]  = { 0x61, 0x62, 0x63, 0x00 };
char* pstr4 = &charArray4[0];
String* szAsciiLower = new String(pstr4, 0, sizeof(charArray4));

// Prints "ABC abc"
Console::WriteLine(String::Concat(szAsciiUpper," ", szAsciiLower));

// Compare Strings - the result is true
Console::WriteLine(String::Concat("The Strings are equal when capitalized ? ",
    (0 == String::Compare(szAsciiUpper->ToUpper(),szAsciiLower->ToUpper())?"TRUE":"FALSE") ));

// This is the effective equivalent of another Compare method, which ignores case
Console::WriteLine(String::Concat("The Strings are equal when capitalized ? ",
    (0 == String::Compare(szAsciiUpper, szAsciiLower, true)?"TRUE":"FALSE") ) );

[Visual Basic, JScript] No example is available for Visual Basic or JScript. To view a C# or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework, Common Language Infrastructure (CLI) Standard

See Also

String Class | String Members | System Namespace | String.Compare Overload List | Int32 | CompareOrdinal | CompareTo | IsPrefix

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