LastIndexOf Method (Char, Int32, Int32)

String.LastIndexOf Method (Char, Int32, Int32)


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

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

public int LastIndexOf(
	char value,
	int startIndex,
	int count


Type: System.Char

The Unicode character to seek.

Type: System.Int32

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

Type: System.Int32

The number of character positions to examine.

Return Value

Type: System.Int32

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

Exception Condition

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.


The current instance does not equal String.Empty, and startIndex - count + 1 is less than zero.

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 and proceeds backward toward the beginning of this instance 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. 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 value 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 substring, working from the end of the substring to the start of the substring.

// Sample for String.LastIndexOf(Char, 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 't' from position {0} to {1}.", start, end);
    Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str);
    Console.Write("The letter 't' 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('t', 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 't' from position 66 to 32.
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


Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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