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CompareInfo.IndexOf Method (String, String, Int32)

Searches for the specified substring and returns the zero-based index of the first occurrence within the section of the source string that extends from the specified index to the end of the string.

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

public virtual int IndexOf(
	string source,
	string value,
	int startIndex
)

Parameters

source
Type: System.String
The string to search.
value
Type: System.String
The string to locate within source.
startIndex
Type: System.Int32
The zero-based starting index of the search.

Return Value

Type: System.Int32
The zero-based index of the first occurrence of value within the section of source that extends from startIndex to the end of source, if found; otherwise, -1.

ExceptionCondition
ArgumentNullException

source is null.

-or-

value is null.

ArgumentOutOfRangeException

startIndex is outside the range of valid indexes for source.

The source string is searched forward starting at startIndex and ending at the end of the string.

This overload performs a culture-sensitive search. A Unicode 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. To perform an ordinal (culture-insensitive) search, where the Unicode values are compared, the application should use one of the overloads that accepts a CompareOptions value as a parameter and use the Ordinal value.

With culture-sensitive searches, if value contains characters that are ignorable, then the search is equivalent to searching for a pattern with all the ignorable characters removed. If this is the empty string, then the return value is the offset of the first character within the searchable section of source.

NoteNote

When possible, the application should use string comparison methods that accept a CompareOptions value to specify the kind of comparison expected. As a general rule, user-facing comparisons are best served by the use of linguistic options (using the current culture), while security comparisons should specify Ordinal or OrdinalIgnoreCase.

The following code example determines the indexes of the first and last occurrences of a character or a substring within a portion of a string. Note that IndexOf and LastIndexOf are searching in different portions of the string, even with the same startIndex parameter.


using System;
using System.Globalization;

public class SamplesCompareInfo  {

   public static void Main()  {

      // Creates CompareInfo for the InvariantCulture.
      CompareInfo myComp = CultureInfo.InvariantCulture.CompareInfo;

      // iS is the starting index of the substring.
      int iS = 20;
      // myT1 is the string used for padding.
      String myT1;

      // Searches for the ligature Æ.
      String myStr = "Is AE or ae the same as Æ or æ?";
      Console.WriteLine();

      myT1 = new String( '-', iS );
      Console.WriteLine( "IndexOf( String, *, {0}, * )", iS );
      Console.WriteLine( "Original      : {0}", myStr );
      Console.WriteLine( "No options    : {0}{1}", myT1, myStr.Substring( iS ) );
      PrintMarker( "           AE : ", myComp.IndexOf( myStr, "AE", iS ), -1 );
      PrintMarker( "           ae : ", myComp.IndexOf( myStr, "ae", iS ), -1 );
      PrintMarker( "            Æ : ", myComp.IndexOf( myStr, 'Æ', iS ), -1 );
      PrintMarker( "            æ : ", myComp.IndexOf( myStr, 'æ', iS ), -1 );
      Console.WriteLine( "Ordinal       : {0}{1}", myT1, myStr.Substring( iS ) );
      PrintMarker( "           AE : ", myComp.IndexOf( myStr, "AE", iS, CompareOptions.Ordinal ), -1 );
      PrintMarker( "           ae : ", myComp.IndexOf( myStr, "ae", iS, CompareOptions.Ordinal ), -1 );
      PrintMarker( "            Æ : ", myComp.IndexOf( myStr, 'Æ', iS, CompareOptions.Ordinal ), -1 );
      PrintMarker( "            æ : ", myComp.IndexOf( myStr, 'æ', iS, CompareOptions.Ordinal ), -1 );
      Console.WriteLine( "IgnoreCase    : {0}{1}", myT1, myStr.Substring( iS ) );
      PrintMarker( "           AE : ", myComp.IndexOf( myStr, "AE", iS, CompareOptions.IgnoreCase ), -1 );
      PrintMarker( "           ae : ", myComp.IndexOf( myStr, "ae", iS, CompareOptions.IgnoreCase ), -1 );
      PrintMarker( "            Æ : ", myComp.IndexOf( myStr, 'Æ', iS, CompareOptions.IgnoreCase ), -1 );
      PrintMarker( "            æ : ", myComp.IndexOf( myStr, 'æ', iS, CompareOptions.IgnoreCase ), -1 );

      myT1 = new String( '-', myStr.Length - iS - 1 );
      Console.WriteLine( "LastIndexOf( String, *, {0}, * )", iS );
      Console.WriteLine( "Original      : {0}", myStr );
      Console.WriteLine( "No options    : {0}{1}", myStr.Substring( 0, iS + 1 ), myT1 );
      PrintMarker( "           AE : ", -1, myComp.LastIndexOf( myStr, "AE", iS ) );
      PrintMarker( "           ae : ", -1, myComp.LastIndexOf( myStr, "ae", iS ) );
      PrintMarker( "            Æ : ", -1, myComp.LastIndexOf( myStr, 'Æ', iS ) );
      PrintMarker( "            æ : ", -1, myComp.LastIndexOf( myStr, 'æ', iS ) );
      Console.WriteLine( "Ordinal       : {0}{1}", myStr.Substring( 0, iS + 1 ), myT1 );
      PrintMarker( "           AE : ", -1, myComp.LastIndexOf( myStr, "AE", iS, CompareOptions.Ordinal ) );
      PrintMarker( "           ae : ", -1, myComp.LastIndexOf( myStr, "ae", iS, CompareOptions.Ordinal ) );
      PrintMarker( "            Æ : ", -1, myComp.LastIndexOf( myStr, 'Æ', iS, CompareOptions.Ordinal ) );
      PrintMarker( "            æ : ", -1, myComp.LastIndexOf( myStr, 'æ', iS, CompareOptions.Ordinal ) );
      Console.WriteLine( "IgnoreCase    : {0}{1}", myStr.Substring( 0, iS + 1 ), myT1 );
      PrintMarker( "           AE : ", -1, myComp.LastIndexOf( myStr, "AE", iS, CompareOptions.IgnoreCase ) );
      PrintMarker( "           ae : ", -1, myComp.LastIndexOf( myStr, "ae", iS, CompareOptions.IgnoreCase ) );
      PrintMarker( "            Æ : ", -1, myComp.LastIndexOf( myStr, 'Æ', iS, CompareOptions.IgnoreCase ) );
      PrintMarker( "            æ : ", -1, myComp.LastIndexOf( myStr, 'æ', iS, CompareOptions.IgnoreCase ) );

      // Searches for the combining character sequence Latin capital letter U with diaeresis or Latin small letter u with diaeresis.
      myStr = "Is \u0055\u0308 or \u0075\u0308 the same as \u00DC or \u00FC?";
      Console.WriteLine();

      myT1 = new String( '-', iS );
      Console.WriteLine( "IndexOf( String, *, {0}, * )", iS );
      Console.WriteLine( "Original      : {0}", myStr );
      Console.WriteLine( "No options    : {0}{1}", myT1, myStr.Substring( iS ) );
      PrintMarker( "           U\u0308 : ", myComp.IndexOf( myStr, "U\u0308", iS ), -1 );
      PrintMarker( "           u\u0308 : ", myComp.IndexOf( myStr, "u\u0308", iS ), -1 );
      PrintMarker( "            Ü : ", myComp.IndexOf( myStr, 'Ü', iS ), -1 );
      PrintMarker( "            ü : ", myComp.IndexOf( myStr, 'ü', iS ), -1 );
      Console.WriteLine( "Ordinal       : {0}{1}", myT1, myStr.Substring( iS ) );
      PrintMarker( "           U\u0308 : ", myComp.IndexOf( myStr, "U\u0308", iS, CompareOptions.Ordinal ), -1 );
      PrintMarker( "           u\u0308 : ", myComp.IndexOf( myStr, "u\u0308", iS, CompareOptions.Ordinal ), -1 );
      PrintMarker( "            Ü : ", myComp.IndexOf( myStr, 'Ü', iS, CompareOptions.Ordinal ), -1 );
      PrintMarker( "            ü : ", myComp.IndexOf( myStr, 'ü', iS, CompareOptions.Ordinal ), -1 );
      Console.WriteLine( "IgnoreCase    : {0}{1}", myT1, myStr.Substring( iS ) );
      PrintMarker( "           U\u0308 : ", myComp.IndexOf( myStr, "U\u0308", iS, CompareOptions.IgnoreCase ), -1 );
      PrintMarker( "           u\u0308 : ", myComp.IndexOf( myStr, "u\u0308", iS, CompareOptions.IgnoreCase ), -1 );
      PrintMarker( "            Ü : ", myComp.IndexOf( myStr, 'Ü', iS, CompareOptions.IgnoreCase ), -1 );
      PrintMarker( "            ü : ", myComp.IndexOf( myStr, 'ü', iS, CompareOptions.IgnoreCase ), -1 );

      myT1 = new String( '-', myStr.Length - iS - 1 );
      Console.WriteLine( "LastIndexOf( String, *, {0}, * )", iS );
      Console.WriteLine( "Original      : {0}", myStr );
      Console.WriteLine( "No options    : {0}{1}", myStr.Substring( 0, iS + 1 ), myT1 );
      PrintMarker( "           U\u0308 : ", -1, myComp.LastIndexOf( myStr, "U\u0308", iS ) );
      PrintMarker( "           u\u0308 : ", -1, myComp.LastIndexOf( myStr, "u\u0308", iS ) );
      PrintMarker( "            Ü : ", -1, myComp.LastIndexOf( myStr, 'Ü', iS ) );
      PrintMarker( "            ü : ", -1, myComp.LastIndexOf( myStr, 'ü', iS ) );
      Console.WriteLine( "Ordinal       : {0}{1}", myStr.Substring( 0, iS + 1 ), myT1 );
      PrintMarker( "           U\u0308 : ", -1, myComp.LastIndexOf( myStr, "U\u0308", iS, CompareOptions.Ordinal ) );
      PrintMarker( "           u\u0308 : ", -1, myComp.LastIndexOf( myStr, "u\u0308", iS, CompareOptions.Ordinal ) );
      PrintMarker( "            Ü : ", -1, myComp.LastIndexOf( myStr, 'Ü', iS, CompareOptions.Ordinal ) );
      PrintMarker( "            ü : ", -1, myComp.LastIndexOf( myStr, 'ü', iS, CompareOptions.Ordinal ) );
      Console.WriteLine( "IgnoreCase    : {0}{1}", myStr.Substring( 0, iS + 1 ), myT1 );
      PrintMarker( "           U\u0308 : ", -1, myComp.LastIndexOf( myStr, "U\u0308", iS, CompareOptions.IgnoreCase ) );
      PrintMarker( "           u\u0308 : ", -1, myComp.LastIndexOf( myStr, "u\u0308", iS, CompareOptions.IgnoreCase ) );
      PrintMarker( "            Ü : ", -1, myComp.LastIndexOf( myStr, 'Ü', iS, CompareOptions.IgnoreCase ) );
      PrintMarker( "            ü : ", -1, myComp.LastIndexOf( myStr, 'ü', iS, CompareOptions.IgnoreCase ) );

   }

   public static void PrintMarker( String Prefix, int First, int Last )  {

      // Determines the size of the array to create.
      int mySize;
      if ( Last > First )
         mySize = Last;
      else
         mySize = First;

      if ( mySize > -1 )  {

         // Creates an array of Char to hold the markers.
         Char[] myCharArr = new Char[mySize+1];

         // Inserts the appropriate markers.
         if ( First > -1 )
         myCharArr[First] = 'f';
         if ( Last > -1 )
            myCharArr[Last] = 'l';
         if ( First == Last )
         myCharArr[First] = 'b';

         // Displays the array of Char as a String.
         Console.WriteLine( "{0}{1}", Prefix, new String( myCharArr ) );

      }
      else
         Console.WriteLine( Prefix );

   }

}


/*
This code produces the following output.

IndexOf( String, *, 20, * )
Original      : Is AE or ae the same as Æ or æ?
No options    : -------------------- as Æ or æ?
           AE :                         f
           ae :                              f
            Æ :                         f
            æ :                              f
Ordinal       : -------------------- as Æ or æ?
           AE :
           ae :
            Æ :                         f
            æ :                              f
IgnoreCase    : -------------------- as Æ or æ?
           AE :                         f
           ae :                         f
            Æ :                         f
            æ :                         f
LastIndexOf( String, *, 20, * )
Original      : Is AE or ae the same as Æ or æ?
No options    : Is AE or ae the same ----------
           AE :    l
           ae :          l
            Æ :    l
            æ :          l
Ordinal       : Is AE or ae the same ----------
           AE :    l
           ae :          l
            Æ :
            æ :
IgnoreCase    : Is AE or ae the same ----------
           AE :          l
           ae :          l
            Æ :          l
            æ :          l

IndexOf( String, *, 20, * )
Original      : Is U" or u" the same as Ü or ü?
No options    : -------------------- as Ü or ü?
           U" :                         f
           u" :                              f
            Ü :                         f
            ü :                              f
Ordinal       : -------------------- as Ü or ü?
           U" :
           u" :
            Ü :                         f
            ü :                              f
IgnoreCase    : -------------------- as Ü or ü?
           U" :                         f
           u" :                         f
            Ü :                         f
            ü :                         f
LastIndexOf( String, *, 20, * )
Original      : Is U" or u" the same as Ü or ü?
No options    : Is U" or u" the same ----------
           U" :    l
           u" :          l
            Ü :    l
            ü :          l
Ordinal       : Is U" or u" the same ----------
           U" :    l
           u" :          l
            Ü :
            ü :
IgnoreCase    : Is U" or u" the same ----------
           U" :          l
           u" :          l
            Ü :          l
            ü :          l

*/


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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