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String.IndexOf Method (Char, Int32)


Reports the zero-based index of the first occurrence of the specified Unicode character in this string. The search starts at a specified character position.

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)

public int IndexOf(
	char value,
	int startIndex


Type: System.Char

A Unicode character to seek.

Type: System.Int32

The search starting position.

Return Value

Type: System.Int32

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

Exception Condition

startIndex is less than 0 (zero) or greater than the length of the string.

Index numbering starts from 0. The startIndex parameter can range from 0 to the length of the string instance. If startIndex equals the length of the string instance, the method returns -1.

The search ranges from startIndex to the end of the string.

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 CompareInfo.IndexOf 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 demonstrates the IndexOf method.

// Sample for String.IndexOf(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;

    Console.WriteLine("All occurrences of 't' from position 0 to {0}.", str.Length-1);
    Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str);
    Console.Write("The letter 't' occurs at position(s): ");

    at = 0;
    start = 0; 
    while((start < str.Length) && (at > -1))
        at = str.IndexOf('t', start);
        if (at == -1) break;
        Console.Write("{0} ", at);
        start = at+1;
This example produces the following results:

All occurrences of 't' from position 0 to 66.
Now is the time for all good men to come to the aid of their party.

The letter 't' occurs at position(s): 7 11 33 41 44 55 64


Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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