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String.LastIndexOf Method (Char, Int32)

Reports the zero-based index position of the last occurrence of a specified Unicode character within this instance. The search starts at a specified character position and proceeds backward toward the beginning of the string.

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

public int LastIndexOf(
	char value,
	int startIndex
)

Parameters

value
Type: System.Char

The Unicode character to seek.

startIndex
Type: System.Int32

The starting position of the search. The search proceeds from startIndex toward the beginning of this instance.

Return Value

Type: System.Int32
The zero-based index position of value if that character is found, or -1 if it is not found or if the current instance equals String.Empty.

ExceptionCondition
ArgumentOutOfRangeException

The current instance does not equal String.Empty, and startIndex is less than zero or greater than or equal to the length of this instance.

Index numbering starts from zero. That is, the first character in the string is at index zero and the last is at Length - 1.This method begins searching at the startIndex character position of this instance and proceeds backward toward the beginning of the current instance until either value is found or the first character position has been examined. For example, if startIndex is Length - 1, the method searches every character from the last character in the string to the beginning. The search is case-sensitive.

This method performs an ordinal (culture-insensitive) search, where a character is considered equivalent to another character only if their Unicode scalar values are the same. To perform a culture-sensitive search, use the CompareInfo.LastIndexOf method, where a Unicode scalar value representing a precomposed character, such as the ligature "Æ" (U+00C6), might be considered equivalent to any occurrence of the character's components in the correct sequence, such as "AE" (U+0041, U+0045), depending on the culture.

The following example finds the index of all occurrences of a character in a string, working from the end of the string to the start of the string.

// Sample for String.LastIndexOf(Char, Int32) 
using System;

class Sample {
    public static void Main() {

    string br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
    string br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
    string str = "Now is the time for all good men to come to the aid of their party.";
    int start;
    int at;

    start = str.Length-1;
    Console.WriteLine("All occurrences of 't' from position {0} to 0.", start);
    Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str);
    Console.Write("The letter 't' occurs at position(s): ");

    at = 0;
    while((start > -1) && (at > -1))
        {
        at = str.LastIndexOf('t', start);
        if (at > -1) 
            {
            Console.Write("{0} ", at);
            start = at - 1;
            }
        }
    Console.Write("{0}{0}{0}", Environment.NewLine);
    }
}
/*
This example produces the following results:
All occurrences of 't' from position 66 to 0.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The letter 't' occurs at position(s): 64 55 44 41 33 11 7
*/

.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

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, 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.

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