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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)

[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.

ExceptionCondition
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 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)

*/


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

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

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