LastIndexOf 方法 (Char, Int32)
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String.LastIndexOf 方法 (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.

命名空間:   System
組件:  mscorlib (在 mscorlib.dll 中)

public int LastIndexOf(
	char value,
	int startIndex


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 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.

Index numbering starts from zero. That is, the first character in the string is at index zero and the last is at P:System.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 P:System.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 M:System.Globalization.CompareInfo.LastIndexOf(System.String,System.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.

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.
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

Universal Windows Platform
自 4.5 起可用
.NET Framework
自 1.1 起可用
Portable Class Library
支援版本:portable .NET platforms
自 2.0 起可用
Windows Phone Silverlight
自 7.0 起可用
Windows Phone
自 8.1 起可用
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