• Article

String.Equals Method (String, StringComparison)

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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)

Syntax

'Declaration
<SecuritySafeCriticalAttribute> _
Public Function Equals ( _
    value As String, _
    comparisonType As StringComparison _
) As Boolean

[SecuritySafeCriticalAttribute]
public bool Equals(
    string value,
    StringComparison comparisonType
)

Parameters

  • value
    Type: System.String
    The string to compare to this instance.
  • comparisonType
    Type: System.StringComparison
    One of the enumeration values that specifies the rules for the comparison.

Return Value

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

Exceptions

Exception Condition
ArgumentException

comparisonType is not a StringComparison value.

Remarks

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.

Examples

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.

Imports System.Threading

Class Example
   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim intro As String = "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.)  
      Dim threeIs(2) As String
      ' LATIN SMALL LETTER I (U+0069)
      threeIs(0) = "i"
      ' LATIN SMALL LETTER DOTLESS I (U+0131)
      threeIs(1) = "ı"
      ' LATIN CAPITAL LETTER I (U+0049)
      threeIs(2) = "I"

      Dim unicodeNames As String() = { _
                           "LATIN SMALL LETTER I (U+0069)", _
                           "LATIN SMALL LETTER DOTLESS I (U+0131)", _
                           "LATIN CAPITAL LETTER I (U+0049)"}

      Dim scValues As StringComparison() = { _
                      StringComparison.CurrentCulture, _
                      StringComparison.CurrentCultureIgnoreCase, _
                      StringComparison.InvariantCulture, _
                      StringComparison.InvariantCultureIgnoreCase, _
                      StringComparison.Ordinal, _
                      StringComparison.OrdinalIgnoreCase}

      outputBlock.Text &= intro & vbCrLf

      ' Display the current culture because the culture-specific comparisons
      ' can produce different results with different cultures.
      outputBlock.Text &= String.Format("The current culture is {0}." & vbCrLf, _
                         Thread.CurrentThread.CurrentCulture.Name) & vbCrLf

      ' Determine whether three versions of the letter I are equal to each other. 
      Dim sc As StringComparison
      For Each sc In scValues
         outputBlock.Text &= String.Format("StringComparison.{0}:", sc) & vbCrLf

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

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

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

         outputBlock.Text &= vbCrLf
      Next sc

   End Sub 'Main

   Protected Shared Sub Test(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal x As Integer, ByVal y As Integer, _
                             ByVal comparison As StringComparison, _
                             ByVal testI() As String, ByVal testNames() As String)
      Dim resultFmt As String = "{0} is {1}equal to {2}"
      Dim result As String = "not "
      '
      If testI(x).Equals(testI(y), comparison) Then
         result = ""
      End If
      outputBlock.Text &= String.Format(resultFmt, testNames(x), result, testNames(y)) & vbCrLf

   End Sub 'Test
End Class 'Sample

'
'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)
'
'

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

using System;
using System.Threading;

class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      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 };

      outputBlock.Text += intro + "\n";

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

      // Determine whether three versions of the letter I are equal to each other. 
      foreach (StringComparison sc in scValues)
      {
         outputBlock.Text += String.Format("StringComparison.{0}:", sc) + "\n";

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

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

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

         outputBlock.Text += "\n";
      }
   }

   protected static void Test(System.Windows.Controls.TextBlock outputBlock, 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 = "";
      outputBlock.Text += String.Format(resultFmt, testNames[x], result, testNames[y]) + "\n";
   }
}

/*
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)

*/

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.