.NET Framework Class Library
StringCompare Method (String, String, Boolean)

Compares 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)
Syntax
Public Shared Function Compare ( _
	strA As [%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_0_0_0%], _
	strB As [%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_0_0_1%], _
	ignoreCase As [%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_0_0_2%] _
) As [%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_0_0_3%]
public static [%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_1_0_0%] Compare(
	[%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_1_0_1%] strA,
	[%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_1_0_2%] strB,
	[%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_1_0_3%] ignoreCase
)
public:
static [%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_2_0_0%] Compare(
	[%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_2_0_1%]^ strA, 
	[%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_2_0_2%]^ strB, 
	[%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_2_0_3%] ignoreCase
)
static member Compare : 
        strA:[%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_3_0_0%] * 
        strB:[%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_3_0_1%] * 
        ignoreCase:[%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_3_0_2%] -> [%$TOPIC/zkcaxw5y_en-us_VS_110_2_0_3_0_3%]

Parameters

strA
Type: SystemString

The first string to compare.

strB
Type: SystemString

The second string to compare.

ignoreCase
Type: SystemBoolean

true to ignore case during the comparison; otherwise, false.

Return Value

Type: SystemInt32
A 32-bit signed integer that indicates the lexical relationship between the two comparands.

Value

Condition

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.GlobalizationCompareOptions.

Caution noteCaution

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

Shared Function IsFileURI(ByVal path As String) As Boolean 
    If String.Compare(path, 0, "file:", 0, 5, True) = 0 Then 
        Return True 
    Else 
        Return False 
    End If 
End Function
static bool IsFileURI(String path)
{
    return (String.Compare(path, 0, "file:", 0, 5, true) == 0);
}
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:

Shared Function IsFileURI(ByVal path As String) As Boolean 
    If String.Compare(path, 0, "file:", 0, 5, StringComparison.OrdinalIgnoreCase) = 0 Then 
        Return True 
    Else 
        Return False 
    End If 
End Function
static bool IsFileURI(String path)
{
    return (String.Compare(path, 0, "file:", 0, 5, StringComparison.OrdinalIgnoreCase) == 0);
}
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, String, Boolean) method does not consider such characters when it performs a culture-sensitive comparison. For example, if the following code is run on the .NET Framework 4 or later, a culture-sensitive, case-insensitive comparison of "animal" with "Ani-mal" (using a soft hyphen, or U+00AD) indicates that the two strings are equivalent.

Module Example
   Public Sub Main()
      Dim s1 As String = "Ani" + ChrW(&h00AD) + "mal" 
      Dim s2 As String = "animal"

      Console.WriteLine("Comparison of '{0}' and '{1}': {2}", 
                        s1, s2, String.Compare(s1, s2, True))
  End Sub 
End Module 
' The example displays the following output: 
'       Comparison of 'ani-mal' and 'animal': 0
using System;

public class Example
{
   public static void Main()
   {
      string s1 = "Ani\u00ADmal";
      string s2 = "animal";

      Console.WriteLine("Comparison of '{0}' and '{1}': {2}", 
                        s1, s2, String.Compare(s1, s2, true));
   }
}
// The example displays the following output: 
//       Comparison of 'ani-mal' and 'animal': 0

To recognize ignorable characters in a string comparison, call the Compare method and supply a value of either CompareOptionsOrdinal or CompareOptionsOrdinalIgnoreCase for the comparisonType parameter.

Examples

The following example demonstrates that the Compare(String, String, Boolean) method is equivalent to using ToUpper or ToLower when comparing strings.

Public Module Example
   Public Sub Main()
      ' Create upper-case characters from their Unicode code units. 
      Dim stringUpper As String = ChrW(&H41) + ChrW(&H42) + ChrW(&H43)

      ' Create lower-case characters from their Unicode code units. 
      Dim stringLower As String = ChrW(&H61) + ChrW(&H62) + ChrW(&H63)

      ' Display the strings.
      Console.WriteLine("Comparing '{0}' and '{1}':", 
                        stringUpper, stringLower)

      ' Compare the uppercased strings; the result is true.
      Console.WriteLine("The Strings are equal when capitalized? {0}",
                        If(String.Compare(stringUpper.ToUpper(), stringLower.ToUpper()) = 0, 
                                          "true", "false"))

      ' The previous method call is equivalent to this Compare method, which ignores case.
      Console.WriteLine("The Strings are equal when case is ignored? {0}",
                        If(String.Compare(stringUpper, stringLower, true) = 0,
                                          "true", "false"))
   End Sub 
End Module  
' The example displays the following output: 
'       Comparing 'ABC' and 'abc': 
'       The Strings are equal when capitalized? true 
'       The Strings are equal when case is ignored? true
using System;

class Example
{
   static void Main()
   {
      // Create upper-case characters from their Unicode code units.
      String stringUpper = "\x0041\x0042\x0043";

      // Create lower-case characters from their Unicode code units.
      String stringLower = "\x0061\x0062\x0063";

      // Display the strings.
      Console.WriteLine("Comparing '{0}' and '{1}':", 
                        stringUpper, stringLower);

      // Compare the uppercased strings; the result is true.
      Console.WriteLine("The Strings are equal when capitalized? {0}",
                        String.Compare(stringUpper.ToUpper(), stringLower.ToUpper()) == 0 
                                       ? "true" : "false");

      // The previous method call is equivalent to this Compare method, which ignores case.
      Console.WriteLine("The Strings are equal when case is ignored? {0}",
                        String.Compare(stringUpper, stringLower, true) == 0
                                       ? "true" : "false" );
   }
} 
// The example displays the following output: 
//       Comparing 'ABC' and 'abc': 
//       The Strings are equal when capitalized? true 
//       The Strings are equal when case is ignored? true
using namespace System;

void main()
{
   // Create upper-case characters from their Unicode code units.
   String^ stringUpper = "\x0041\x0042\x0043";

   // Create lower-case characters from their Unicode code units.
   String^ stringLower = "\x0061\x0062\x0063";

   // Display the strings.
   Console::WriteLine("Comparing '{0}' and '{1}':", 
                      stringUpper, stringLower);

   // Compare the uppercased strings; the result is true.
   Console::WriteLine("The Strings are equal when capitalized? {0}",
                      String::Compare(stringUpper->ToUpper(), stringLower->ToUpper()) == 0 
                                      ? "true" : "false");

   // The previous method call is equivalent to this Compare method, which ignores case.
   Console::WriteLine("The Strings are equal when case is ignored? {0}",
                      String::Compare(stringUpper, stringLower, true) == 0
                                      ? "true" : "false");
}
// The example displays the following output: 
//       Comparing 'ABC' and 'abc': 
//       The Strings are equal when capitalized? true 
//       The Strings are equal when case is ignored? true
Version Information

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
Platforms

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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