System.String.LastIndexOf Method

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.

Syntax

public int LastIndexOf (char value, int startIndex)

Parameters

value
The Unicode character to seek.
startIndex
The starting position of the search. The search proceeds from startIndex toward the beginning of this instance.

Returns

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.

Exceptions

TypeReason
ArgumentNullException value is a null reference.
ArgumentOutOfRangeException startIndex is less than zero or greater than the length of the current instance.

Remarks

Index numbering starts from zero. That is, the first character in the string is at index zero and the last is at string.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 string.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 System.Globalization.CompareInfo.LastIndexOf(string, char) 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.

Example

The following example demonstrates the string.LastIndexOf(char) method.

C# Example

using System;
public class StringLastIndexOfTest {
   public static void Main() {
      String str = "aa bb cc dd";
      
      Console.WriteLine( str.LastIndexOf('d', 8) );
      Console.WriteLine( str.LastIndexOf('b', 8) );
   }
}

The output is

-1
4

Requirements

Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0