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CompareInfo.LastIndexOf Method (String, Char)

Searches for the specified character and returns the zero-based index of the last occurrence within the entire source string.

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

public virtual int LastIndexOf(
	string source,
	char value
)

Parameters

source
Type: System.String
The string to search.
value
Type: System.Char
The character to locate within source.

Return Value

Type: System.Int32
The zero-based index of the last occurrence of value within the entire source, if found; otherwise, -1.

ExceptionCondition
ArgumentNullException

source is null.

The source string is searched backward starting at the end of the string and ending at the beginning of the string.

This overload performs a culture-sensitive search. If the character is a Unicode value representing a precomposed character, such as the ligature "Æ" (U+00C6), it might be considered equivalent to any occurrence of its components in the correct sequence, such as "AE" (U+0041, U+0045), depending on the culture. To perform an ordinal (culture-insensitive) search, where a character is considered equivalent to another character only if the Unicode values are the same, the application should use one of the overloads that accepts a CompareOptions value as a parameter and use the Ordinal value. Overloads of String.LastIndexOf that search for a character perform an ordinal search, while those that search for a string perform a culture-sensitive search.

NoteNote

When possible, the application should use string comparison methods that accept a CompareOptions value to specify the kind of comparison expected. As a general rule, user-facing comparisons are best served by the use of linguistic options (using the current culture), while security comparisons should specify Ordinal or OrdinalIgnoreCase.

The following code example determines the indexes of the first and last occurrences of a character or a substring within a string.


using System;
using System.Globalization;

public class SamplesCompareInfo  {

   public static void Main()  {

      // Creates CompareInfo for the InvariantCulture.
      CompareInfo myComp = CultureInfo.InvariantCulture.CompareInfo;

      // Searches for the ligature Æ.
      String myStr = "Is AE or ae the same as Æ or æ?";
      Console.WriteLine();
      Console.WriteLine( "No options    : {0}", myStr );
      PrintMarker( "           AE : ", myComp.IndexOf( myStr, "AE" ), myComp.LastIndexOf( myStr, "AE" ) );
      PrintMarker( "           ae : ", myComp.IndexOf( myStr, "ae" ), myComp.LastIndexOf( myStr, "ae" ) );
      PrintMarker( "            Æ : ", myComp.IndexOf( myStr, 'Æ' ), myComp.LastIndexOf( myStr, 'Æ' ) );
      PrintMarker( "            æ : ", myComp.IndexOf( myStr, 'æ' ), myComp.LastIndexOf( myStr, 'æ' ) );
      Console.WriteLine( "Ordinal       : {0}", myStr );
      PrintMarker( "           AE : ", myComp.IndexOf( myStr, "AE", CompareOptions.Ordinal ), myComp.LastIndexOf( myStr, "AE", CompareOptions.Ordinal ) );
      PrintMarker( "           ae : ", myComp.IndexOf( myStr, "ae", CompareOptions.Ordinal ), myComp.LastIndexOf( myStr, "ae", CompareOptions.Ordinal ) );
      PrintMarker( "            Æ : ", myComp.IndexOf( myStr, 'Æ', CompareOptions.Ordinal ), myComp.LastIndexOf( myStr, 'Æ', CompareOptions.Ordinal ) );
      PrintMarker( "            æ : ", myComp.IndexOf( myStr, 'æ', CompareOptions.Ordinal ), myComp.LastIndexOf( myStr, 'æ', CompareOptions.Ordinal ) );
      Console.WriteLine( "IgnoreCase    : {0}", myStr );
      PrintMarker( "           AE : ", myComp.IndexOf( myStr, "AE", CompareOptions.IgnoreCase ), myComp.LastIndexOf( myStr, "AE", CompareOptions.IgnoreCase ) );
      PrintMarker( "           ae : ", myComp.IndexOf( myStr, "ae", CompareOptions.IgnoreCase ), myComp.LastIndexOf( myStr, "ae", CompareOptions.IgnoreCase ) );
      PrintMarker( "            Æ : ", myComp.IndexOf( myStr, 'Æ', CompareOptions.IgnoreCase ), myComp.LastIndexOf( myStr, 'Æ', CompareOptions.IgnoreCase ) );
      PrintMarker( "            æ : ", myComp.IndexOf( myStr, 'æ', CompareOptions.IgnoreCase ), myComp.LastIndexOf( myStr, 'æ', CompareOptions.IgnoreCase ) );

      // Searches for the combining character sequence Latin capital letter U with diaeresis or Latin small letter u with diaeresis.
      myStr = "Is \u0055\u0308 or \u0075\u0308 the same as \u00DC or \u00FC?";
      Console.WriteLine();
      Console.WriteLine( "No options    : {0}", myStr );
      PrintMarker( "           U\u0308 : ", myComp.IndexOf( myStr, "U\u0308" ), myComp.LastIndexOf( myStr, "U\u0308" ) );
      PrintMarker( "           u\u0308 : ", myComp.IndexOf( myStr, "u\u0308" ), myComp.LastIndexOf( myStr, "u\u0308" ) );
      PrintMarker( "            Ü : ", myComp.IndexOf( myStr, 'Ü' ), myComp.LastIndexOf( myStr, 'Ü' ) );
      PrintMarker( "            ü : ", myComp.IndexOf( myStr, 'ü' ), myComp.LastIndexOf( myStr, 'ü' ) );
      Console.WriteLine( "Ordinal       : {0}", myStr );
      PrintMarker( "           U\u0308 : ", myComp.IndexOf( myStr, "U\u0308", CompareOptions.Ordinal ), myComp.LastIndexOf( myStr, "U\u0308", CompareOptions.Ordinal ) );
      PrintMarker( "           u\u0308 : ", myComp.IndexOf( myStr, "u\u0308", CompareOptions.Ordinal ), myComp.LastIndexOf( myStr, "u\u0308", CompareOptions.Ordinal ) );
      PrintMarker( "            Ü : ", myComp.IndexOf( myStr, 'Ü', CompareOptions.Ordinal ), myComp.LastIndexOf( myStr, 'Ü', CompareOptions.Ordinal ) );
      PrintMarker( "            ü : ", myComp.IndexOf( myStr, 'ü', CompareOptions.Ordinal ), myComp.LastIndexOf( myStr, 'ü', CompareOptions.Ordinal ) );
      Console.WriteLine( "IgnoreCase    : {0}", myStr );
      PrintMarker( "           U\u0308 : ", myComp.IndexOf( myStr, "U\u0308", CompareOptions.IgnoreCase ), myComp.LastIndexOf( myStr, "U\u0308", CompareOptions.IgnoreCase ) );
      PrintMarker( "           u\u0308 : ", myComp.IndexOf( myStr, "u\u0308", CompareOptions.IgnoreCase ), myComp.LastIndexOf( myStr, "u\u0308", CompareOptions.IgnoreCase ) );
      PrintMarker( "            Ü : ", myComp.IndexOf( myStr, 'Ü', CompareOptions.IgnoreCase ), myComp.LastIndexOf( myStr, 'Ü', CompareOptions.IgnoreCase ) );
      PrintMarker( "            ü : ", myComp.IndexOf( myStr, 'ü', CompareOptions.IgnoreCase ), myComp.LastIndexOf( myStr, 'ü', CompareOptions.IgnoreCase ) );

   }

   public static void PrintMarker( String Prefix, int First, int Last )  {

      // Determines the size of the array to create.
      int mySize;
      if ( Last > First )
         mySize = Last;
      else
         mySize = First;

      if ( mySize > -1 )  {

         // Creates an array of Char to hold the markers.
         Char[] myCharArr = new Char[mySize+1];

         // Inserts the appropriate markers.
         if ( First > -1 )
         myCharArr[First] = 'f';
         if ( Last > -1 )
            myCharArr[Last] = 'l';
         if ( First == Last )
         myCharArr[First] = 'b';

         // Displays the array of Char as a String.
         Console.WriteLine( "{0}{1}", Prefix, new String( myCharArr ) );

      }
      else
         Console.WriteLine( Prefix );

   }

}


/*
This code produces the following output.

No options    : Is AE or ae the same as Æ or æ?
           AE :    f                    l
           ae :          f                   l
            Æ :    f                    l
            æ :          f                   l
Ordinal       : Is AE or ae the same as Æ or æ?
           AE :    b
           ae :          b
            Æ :                         b
            æ :                              b
IgnoreCase    : Is AE or ae the same as Æ or æ?
           AE :    f                         l
           ae :    f                         l
            Æ :    f                         l
            æ :    f                         l

No options    : Is U" or u" the same as Ü or ü?
           U" :    f                    l
           u" :          f                   l
            Ü :    f                    l
            ü :          f                   l
Ordinal       : Is U" or u" the same as Ü or ü?
           U" :    b
           u" :          b
            Ü :                         b
            ü :                              b
IgnoreCase    : Is U" or u" the same as Ü or ü?
           U" :    f                         l
           u" :    f                         l
            Ü :    f                         l
            ü :    f                         l

*/


.NET Framework

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

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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