This documentation is archived and is not being maintained.

String.IndexOf Method (Char, Int32, Int32)

.NET Framework 1.1

Reports the index of the first occurrence of the specified character in this instance. The search starts at a specified character position and examines a specified number of character positions.

[Visual Basic]
Overloads Public Function IndexOf( _
   ByVal value As Char, _
   ByVal startIndex As Integer, _
   ByVal count As Integer _
) As Integer
[C#]
public int IndexOf(
 char value,
 int startIndex,
 int count
);
[C++]
public: int IndexOf(
 __wchar_t value,
 int startIndex,
 int count
);
[JScript]
public function IndexOf(
   value : Char,
 startIndex : int,
 count : int
) : int;

Parameters

value
A Unicode character to seek.
startIndex
The search starting position.
count
The number of character positions to examine.

Return Value

The index position of value if that character is found, or -1 if it is not.

Exceptions

Exception Type Condition
ArgumentOutOfRangeException count or startIndex is negative.

-or-

count + startIndex specifies a position beyond the end of this instance.

Remarks

The search begins at startIndex and continues to startIndex + count-1. The character at startIndex + count is not included in the search.

Index numbering starts from zero.

The search for value 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.IndexOf method, where a Unicode scalar value representing a precomposed character, such as the ligature '' (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

[Visual Basic, C#, C++] The following example demonstrates the IndexOf method.

[Visual Basic] 
' Example for the String.IndexOf( Char, Integer, Integer ) method.
Imports System
Imports Microsoft.VisualBasic

Module IndexOfCII
   
    Sub Main()
        Dim br1 As String = _
            "0----+----1----+----2----+----3----+----" & _
            "4----+----5----+----6----+----7"
        Dim br2 As String = _
            "0123456789012345678901234567890123456789" & _
            "0123456789012345678901234567890"
        Dim str As String = _
            "ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi " & _
            "ABCDEFGHI abcdefghi ABCDEFGHI"
          
        Console.WriteLine( _
            "This example of String.IndexOf( Char, Integer, Integer )" & _
            vbCrLf & "generates the following output." )
        Console.WriteLine( _
            "{0}{1}{0}{2}{0}{3}{0}", _
            Environment.NewLine, br1, br2, str)

        FindAllChar("A"c, str)
        FindAllChar("a"c, str)
        FindAllChar("I"c, str)
        FindAllChar("i"c, str)
        FindAllChar("@"c, str)
        FindAllChar(" "c, str)
    End Sub 'Main
       
    Sub FindAllChar(target As Char, searched As String)

        Console.Write( _
            "The character ""{0}"" occurs at position(s): ", target)
          
        Dim startIndex As Integer = - 1
        Dim hitCount As Integer = 0
          
        ' Search for all occurrences of the target.
        While True
            startIndex = searched.IndexOf( _
                target, startIndex + 1, _
                searched.Length - startIndex - 1)

            ' Exit the loop if the target is not found.
            If startIndex < 0 Then
                Exit While
            End If 

            Console.Write("{0}, ", startIndex)
            hitCount += 1
        End While
          
        Console.WriteLine("occurrences: {0}", hitCount)

    End Sub 'FindAllChar
End Module 'IndexOfCII

' This example of String.IndexOf( Char, Integer, Integer )
' generates the following output.
' 
' 0----+----1----+----2----+----3----+----4----+----5----+----6----+----7
' 01234567890123456789012345678901234567890123456789012345678901234567890
' ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi ABCDEFGHI
' 
' The character "A" occurs at position(s): 0, 20, 40, 60, occurrences: 4
' The character "a" occurs at position(s): 10, 30, 50, occurrences: 3
' The character "I" occurs at position(s): 8, 28, 48, 68, occurrences: 4
' The character "i" occurs at position(s): 18, 38, 58, occurrences: 3
' The character "@" occurs at position(s): occurrences: 0
' The character " " occurs at position(s): 9, 19, 29, 39, 49, 59, occurrences: 6

[C#] 
// Example for the String.IndexOf( char, int, int ) method.
using System;

class IndexOfCII 
{
    public static void Main() 
    {
        string br1 = 
            "0----+----1----+----2----+----3----+----" +
            "4----+----5----+----6----+----7";
        string br2 = 
            "0123456789012345678901234567890123456789" +
            "0123456789012345678901234567890";
        string str = 
            "ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi " +
            "ABCDEFGHI abcdefghi ABCDEFGHI";

        Console.WriteLine( 
            "This example of String.IndexOf( char, int, int )\n" +
            "generates the following output." );
        Console.WriteLine( 
            "{0}{1}{0}{2}{0}{3}{0}", 
            Environment.NewLine, br1, br2, str );

        FindAllChar( 'A', str );
        FindAllChar( 'a', str );
        FindAllChar( 'I', str );
        FindAllChar( 'i', str );
        FindAllChar( '@', str );
        FindAllChar( ' ', str );
    }

    static void FindAllChar( Char target, String searched )
    {
        Console.Write( 
            "The character '{0}' occurs at position(s): ", 
            target );

        int     startIndex = -1;
        int     hitCount = 0;

        // Search for all occurrences of the target.
        while( true )
        {
            startIndex = searched.IndexOf( 
                target, startIndex + 1, 
                searched.Length - startIndex - 1 );

            // Exit the loop if the target is not found.
            if( startIndex < 0 )
                break;

            Console.Write( "{0}, ", startIndex );
            hitCount++;
        }

        Console.WriteLine( "occurrences: {0}", hitCount );
    }
}

/*
This example of String.IndexOf( char, int, int )
generates the following output.

0----+----1----+----2----+----3----+----4----+----5----+----6----+----7
01234567890123456789012345678901234567890123456789012345678901234567890
ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi ABCDEFGHI

The character 'A' occurs at position(s): 0, 20, 40, 60, occurrences: 4
The character 'a' occurs at position(s): 10, 30, 50, occurrences: 3
The character 'I' occurs at position(s): 8, 28, 48, 68, occurrences: 4
The character 'i' occurs at position(s): 18, 38, 58, occurrences: 3
The character '@' occurs at position(s): occurrences: 0
The character ' ' occurs at position(s): 9, 19, 29, 39, 49, 59, occurrences: 6
*/

[C++] 
// Example for the String::IndexOf( Char, int, int ) method.
#using <mscorlib.dll>
using namespace System;

void FindAllChar( Char target, String* searched )
{
    Console::Write( 
        S"The character '{0}' occurs at position(s): ", 
        __box( target ) );

    int     startIndex = -1;
    int     hitCount = 0;

    // Search for all occurrences of the target.
    while( true )
    {
        startIndex = searched->IndexOf( 
            target, startIndex + 1, 
            searched->Length - startIndex - 1 );

        // Exit the loop if the target is not found.
        if( startIndex < 0 )
            break;

        Console::Write( S"{0}, ", __box( startIndex ) );
        hitCount++;
    }

    Console::WriteLine( S"occurrences: {0}", __box( hitCount ) );
}

void main() 
{
    String* br1 = 
        S"0----+----1----+----2----+----3----+----"
        S"4----+----5----+----6----+----7";
    String* br2 = 
        S"0123456789012345678901234567890123456789"
        S"0123456789012345678901234567890";
    String* str = 
        S"ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi "
        S"ABCDEFGHI abcdefghi ABCDEFGHI";

    Console::WriteLine( 
        S"This example of String::IndexOf( Char, int, int )\n" 
        S"generates the following output." );
    Console::WriteLine( 
        S"{0}{1}{0}{2}{0}{3}{0}", 
        Environment::NewLine, br1, br2, str );

    FindAllChar( 'A', str );
    FindAllChar( 'a', str );
    FindAllChar( 'I', str );
    FindAllChar( 'i', str );
    FindAllChar( '@', str );
    FindAllChar( ' ', str );
}

/*
This example of String::IndexOf( Char, int, int )
generates the following output.

0----+----1----+----2----+----3----+----4----+----5----+----6----+----7
01234567890123456789012345678901234567890123456789012345678901234567890
ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi ABCDEFGHI

The character 'A' occurs at position(s): 0, 20, 40, 60, occurrences: 4
The character 'a' occurs at position(s): 10, 30, 50, occurrences: 3
The character 'I' occurs at position(s): 8, 28, 48, 68, occurrences: 4
The character 'i' occurs at position(s): 18, 38, 58, occurrences: 3
The character '@' occurs at position(s): occurrences: 0
The character ' ' occurs at position(s): 9, 19, 29, 39, 49, 59, occurrences: 6
*/

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework, Common Language Infrastructure (CLI) Standard

See Also

String Class | String Members | System Namespace | String.IndexOf Overload List | Char | Int32 | IndexOfAny | LastIndexOf | LastIndexOfAny

Show: