EN
Ce contenu n’est pas disponible dans votre langue. Voici la version anglaise.
Ce sujet n'a pas encore été évalué - Évaluez ce sujet

String.LastIndexOf Method (Char, Int32, Int32)

April 12, 2014

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
)

Parameters

value
Type: System.Char
A Unicode character to seek.
startIndex
Type: System.Int32
The starting position of a substring within this instance. The search proceeds from startIndex toward the beginning of this instance.
count
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 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.

-or-

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 0 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 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 code 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 Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {

      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;
      outputBlock.Text += String.Format("All occurrences of 't' from position {0} to {1}.", start, end) + "\n";
      outputBlock.Text += String.Format("{1}{0}{2}{0}{3}{0}", "\n", br1, br2, str) + "\n";
      outputBlock.Text += "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)
         {
            outputBlock.Text += String.Format("{0} ", at);
            start = at - 1;
         }
      }
      outputBlock.Text += String.Format("{0}{0}{0}", "\n");
   }
}
/*
This example produces the following results:
All occurrences of 't' 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 letter 't' occurs at position(s): 64 55 44 41 33


*/


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

Cela vous a-t-il été utile ?
(1500 caractères restants)
Merci pour vos suggestions.
Afficher:
© 2014 Microsoft. Tous droits réservés.