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String.LastIndexOf Method (String, Int32, Int32)

Updated: July 2008

Reports the index position of the last occurrence of a specified String within this instance. The search starts at a specified character position and examines a specified number of character positions.

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

public int LastIndexOf(
	string value,
	int startIndex,
	int count
)

Parameters

value
Type: System.String

The String to seek.

startIndex
Type: System.Int32

The search starting position.

count
Type: System.Int32

The number of character positions to examine.

Return Value

Type: System.Int32
The index position of value if that string is found, or -1 if it is not found or if the current instance equals String.Empty. If value is Empty, the return value is startIndex.

ExceptionCondition
ArgumentNullException

value is null.

ArgumentOutOfRangeException

The current instance does not equal String.Empty and count or startIndex is negative.

-or-

startIndex is greater than the length of this instance.

-or-

startIndex + 1 - count specifies a position that is not within 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.

The search begins at the startIndex character position of this instance and proceeds backward toward the beginning until either value is found or count character positions have been examined. For example, if startIndex is Length - 1, the method searches backward count characters from the last character in the string.

This method performs a word (case-sensitive and culture-sensitive) search using the current culture.

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

// Sample for String.LastIndexOf(String, Int32, 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;
    int count;
    int end;

    start = str.Length-1;
    end = start/2 - 1;
    Console.WriteLine("All occurrences of 'he' from position {0} to {1}.", start, end);
    Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str);
    Console.Write("The string 'he' occurs at position(s): ");

    count = 0;
    at = 0;
    while((start > -1) && (at > -1))
        {
        count = start - end; //Count must be within the substring.
        at = str.LastIndexOf("he", start, count);
        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 'he' from position 66 to 32.
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 string 'he' occurs at position(s): 56 45
*/

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

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

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Date

History

Reason

July 2008

Added exception information.

Content bug fix.

Community Additions

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