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String.IndexOf Method (String, Int32, Int32)

Reports the index of the first occurrence of the specified String in 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 IndexOf (
	string value,
	int startIndex,
	int count
)
public int IndexOf (
	String value, 
	int startIndex, 
	int count
)
public function IndexOf (
	value : String, 
	startIndex : int, 
	count : int
) : int
Not applicable.

Parameters

value

The String to seek.

startIndex

The search starting position.

count

The number of character positions to examine.

Return Value

The index position of value if that string is found, or -1 if it is not. If value is Empty, the return value is startIndex.

Exception typeCondition

ArgumentNullException

value is a null reference (Nothing in Visual Basic).

ArgumentOutOfRangeException

count or startIndex is negative.

-or-

count plus startIndex specify a position not within this instance.

Index numbering starts from zero.

This method performs a word (case-sensitive and culture-sensitive) search using the current culture. The search begins at startIndex and continues to startIndex + count -1. The character at startIndex + count is not included in the search.

The following code example finds the index of all occurrences of the string "he" within a substring of another string. Note that the number of characters to be searched must be recalculated for each search iteration.

// Sample for String.IndexOf(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 end;
    int count;

    end = str.Length;
    start = end/2;
    Console.WriteLine();
    Console.WriteLine("All occurrences of 'he' from position {0} to {1}.", start, end-1);
    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 <= end) && (at > -1))
        {
// start+count must be a position within -str-.
        count = end - start;
        at = str.IndexOf("he", start, count);
        if (at == -1) break;
        Console.Write("{0} ", at);
        start = at+1;
        }
    Console.WriteLine();
    }
}
/*
This example produces the following results:

All occurrences of 'he' from position 33 to 66.
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): 45 56

*/

// Sample for String.IndexOf(String, Int32, Int32)
import System.*;

class Sample
{
    public static void main(String[] args)
    {
        String br1 = "0----+----1----+----2----+----3----+----4----+----5----"
            + "+----6----+-";
        String br2 = "01234567890123456789012345678901234567890123456789012345"
            + "67890123456";
        String str = "Now is the time for all good men to come to the aid of "
            + "their party.";
        int start;
        int at;
        int end;
        int count;

        end = str.get_Length();
        start = end / 2;
        Console.WriteLine();
        Console.WriteLine("All occurrences of 'he' from position {0} to {1}.",
            (Int32)start, (Int32)(end - 1));
        Console.Write("{1}{0}", Environment.get_NewLine(), br1);
        Console.Write("{1}{0}", Environment.get_NewLine(), br2);
        Console.WriteLine("{1}{0}", Environment.get_NewLine(), str);
        Console.Write("The string 'he' occurs at position(s): ");

        count = 0;
        at = 0;
        while (start <= end && at > -1) {
            // start+count must be a position within -str-.
            count = end - start;
            at = str.IndexOf("he", start, count);
            if (at == -1) {
                break;
            }
            Console.Write("{0} ", (Int32)at);
            start = at + 1;
        }
        Console.WriteLine();
    } //main
} //Sample
/*
This example produces the following results:

All occurrences of 'he' from position 33 to 66.
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): 45 56

*/

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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