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String.IndexOf Method (Char)

Reports the zero-based index of the first occurrence of the specified Unicode character in this string.

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

public int IndexOf(
	char value
)

Parameters

value
Type: System.Char

A Unicode character to seek.

Return Value

Type: System.Int32
The zero-based index position of value if that character is found, or -1 if it is not.

Index numbering starts from zero.

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 how you can search a String for a character using the IndexOf method.

using System;

class Example
{
   static void Main()
   {
      // Create a Unicode string with 5 Greek Alpha characters.
      String szGreekAlpha = new String('\u0391',5);

      // Create a Unicode string with 3 Greek Omega characters.
      String szGreekOmega = "\u03A9\u03A9\u03A9";

      String szGreekLetters = String.Concat(szGreekOmega, szGreekAlpha, 
                                            szGreekOmega.Clone());

      // Display the entire string.
      Console.WriteLine("The string: {0}", szGreekLetters);

      // The first index of Alpha. 
      int ialpha = szGreekLetters.IndexOf('\u0391');
      // The first index of Omega. 
      int iomega = szGreekLetters.IndexOf('\u03A9');

      Console.WriteLine("First occurrence of the Greek letter Alpha: Index {0}", 
                        ialpha);
      Console.WriteLine("First occurrence of the Greek letter Omega: Index {0}", 
                        iomega);
   }
} 
// The example displays the following output: 
//    The string: OOO?????OOO 
//    First occurrence of the Greek letter Alpha: Index 3 
//    First occurrence of the Greek letter Omega: Index 0

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
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