CompareInfo::LastIndexOf Method (String, Char, Int32, Int32)
Searches for the specified character and returns the zero-based index of the last occurrence within the section of the source string that contains the specified number of elements and ends at the specified index.
Assembly: mscorlib (in mscorlib.dll)
public: virtual int LastIndexOf( String^ source, wchar_t value, int startIndex, int count )
Parameters
- source
- Type: System::String
The string to search.
- value
- Type: System::Char
The character to locate within source.
- startIndex
- Type: System::Int32
The zero-based starting index of the backward search.
- count
- Type: System::Int32
The number of elements in the section to search.
Return Value
Type: System::Int32The zero-based index of the last occurrence of value within the section of source that contains the number of elements specified by count and ends at startIndex, if found; otherwise, -1.
| Exception | Condition |
|---|---|
| ArgumentNullException | source is nullptr. |
| ArgumentOutOfRangeException | startIndex is outside the range of valid indexes for source. -or- count is less than zero. -or- startIndex and count do not specify a valid section in source. |
The source string is searched backward starting at startIndex and ending at startIndex - count + 1.
This overload performs a culture-sensitive search. If the character is a Unicode value representing a precomposed character, such as the ligature "Æ" (U+00C6), it might be considered equivalent to any occurrence of its components in the correct sequence, such as "AE" (U+0041, U+0045), depending on the culture. To perform an ordinal (culture-insensitive) search, where a character is considered equivalent to another character only if the Unicode values are the same, the application should use one of the overloads that accepts a CompareOptions value as a parameter and use the Ordinal value. Overloads of String::LastIndexOf that search for a character perform an ordinal search, while those that search for a string perform a culture-sensitive search.
Note |
|---|
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.
using namespace System; using namespace System::Globalization; 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. array<Char>^myCharArr = gcnew array<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, gcnew String( myCharArr ) ); } else Console::WriteLine( Prefix ); } int main() { // Creates CompareInfo for the InvariantCulture. CompareInfo^ myComp = CultureInfo::InvariantCulture->CompareInfo; // iS is the starting index of the substring. int iS = 8; // iL is the length of the substring. int iL = 18; // myT1 and myT2 are the strings used for padding. String^ myT1 = gcnew String( '-',iS ); String^ myT2; // Searches for the ligature Æ. String^ myStr = "Is AE or ae the same as Æ or æ?"; myT2 = gcnew String( '-',myStr->Length - iS - iL ); Console::WriteLine(); Console::WriteLine( "Original : {0}", myStr ); Console::WriteLine( "No options : {0}{1}{2}", myT1, myStr->Substring( iS, iL ), myT2 ); PrintMarker( " AE : ", myComp->IndexOf( myStr, "AE", iS, iL ), myComp->LastIndexOf( myStr, "AE", iS + iL - 1, iL ) ); PrintMarker( " ae : ", myComp->IndexOf( myStr, "ae", iS, iL ), myComp->LastIndexOf( myStr, "ae", iS + iL - 1, iL ) ); PrintMarker( " Æ : ", myComp->IndexOf( myStr, L'Æ', iS, iL ), myComp->LastIndexOf( myStr, L'Æ', iS + iL - 1, iL ) ); PrintMarker( " æ : ", myComp->IndexOf( myStr, L'æ', iS, iL ), myComp->LastIndexOf( myStr, L'æ', iS + iL - 1, iL ) ); Console::WriteLine( "Ordinal : {0}{1}{2}", myT1, myStr->Substring( iS, iL ), myT2 ); PrintMarker( " AE : ", myComp->IndexOf( myStr, "AE", iS, iL, CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, "AE", iS + iL - 1, iL, CompareOptions::Ordinal ) ); PrintMarker( " ae : ", myComp->IndexOf( myStr, "ae", iS, iL, CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, "ae", iS + iL - 1, iL, CompareOptions::Ordinal ) ); PrintMarker( " Æ : ", myComp->IndexOf( myStr, L'Æ', iS, iL, CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, L'Æ', iS + iL - 1, iL, CompareOptions::Ordinal ) ); PrintMarker( " æ : ", myComp->IndexOf( myStr, L'æ', iS, iL, CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, L'æ', iS + iL - 1, iL, CompareOptions::Ordinal ) ); Console::WriteLine( "IgnoreCase : {0}{1}{2}", myT1, myStr->Substring( iS, iL ), myT2 ); PrintMarker( " AE : ", myComp->IndexOf( myStr, "AE", iS, iL, CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, "AE", iS + iL - 1, iL, CompareOptions::IgnoreCase ) ); PrintMarker( " ae : ", myComp->IndexOf( myStr, "ae", iS, iL, CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, "ae", iS + iL - 1, iL, CompareOptions::IgnoreCase ) ); PrintMarker( " Æ : ", myComp->IndexOf( myStr, L'Æ', iS, iL, CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, L'Æ', iS + iL - 1, iL, CompareOptions::IgnoreCase ) ); PrintMarker( " æ : ", myComp->IndexOf( myStr, L'æ', iS, iL, CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, L'æ', iS + iL - 1, iL, CompareOptions::IgnoreCase ) ); // Searches for the combining character sequence Latin capital letter U with diaeresis or Latin small letter u with diaeresis. myStr = "Is U\u0308 or u\u0308 the same as \u00DC or \u00FC?"; myT2 = gcnew String( '-',myStr->Length - iS - iL ); Console::WriteLine(); Console::WriteLine( "Original : {0}", myStr ); Console::WriteLine( "No options : {0}{1}{2}", myT1, myStr->Substring( iS, iL ), myT2 ); PrintMarker( " U\u0308 : ", myComp->IndexOf( myStr, "U\u0308", iS, iL ), myComp->LastIndexOf( myStr, "U\u0308", iS + iL - 1, iL ) ); PrintMarker( " u\u0308 : ", myComp->IndexOf( myStr, "u\u0308", iS, iL ), myComp->LastIndexOf( myStr, "u\u0308", iS + iL - 1, iL ) ); PrintMarker( " Ü : ", myComp->IndexOf( myStr, L'Ü', iS, iL ), myComp->LastIndexOf( myStr, L'Ü', iS + iL - 1, iL ) ); PrintMarker( " ü : ", myComp->IndexOf( myStr, L'ü', iS, iL ), myComp->LastIndexOf( myStr, L'ü', iS + iL - 1, iL ) ); Console::WriteLine( "Ordinal : {0}{1}{2}", myT1, myStr->Substring( iS, iL ), myT2 ); PrintMarker( " U\u0308 : ", myComp->IndexOf( myStr, "U\u0308", iS, iL, CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, "U\u0308", iS + iL - 1, iL, CompareOptions::Ordinal ) ); PrintMarker( " u\u0308 : ", myComp->IndexOf( myStr, "u\u0308", iS, iL, CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, "u\u0308", iS + iL - 1, iL, CompareOptions::Ordinal ) ); PrintMarker( " Ü : ", myComp->IndexOf( myStr, L'Ü', iS, iL, CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, L'Ü', iS + iL - 1, iL, CompareOptions::Ordinal ) ); PrintMarker( " ü : ", myComp->IndexOf( myStr, L'ü', iS, iL, CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, L'ü', iS + iL - 1, iL, CompareOptions::Ordinal ) ); Console::WriteLine( "IgnoreCase : {0}{1}{2}", myT1, myStr->Substring( iS, iL ), myT2 ); PrintMarker( " U\u0308 : ", myComp->IndexOf( myStr, "U\u0308", iS, iL, CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, "U\u0308", iS + iL - 1, iL, CompareOptions::IgnoreCase ) ); PrintMarker( " u\u0308 : ", myComp->IndexOf( myStr, "u\u0308", iS, iL, CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, "u\u0308", iS + iL - 1, iL, CompareOptions::IgnoreCase ) ); PrintMarker( " Ü : ", myComp->IndexOf( myStr, L'Ü', iS, iL, CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, L'Ü', iS + iL - 1, iL, CompareOptions::IgnoreCase ) ); PrintMarker( " ü : ", myComp->IndexOf( myStr, L'ü', iS, iL, CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, L'ü', iS + iL - 1, iL, CompareOptions::IgnoreCase ) ); } /* This code produces the following output. Original : Is AE or ae the same as Æ or æ? No options : -------- ae the same as Æ ----- AE : b ae : b Æ : b æ : b Ordinal : -------- ae the same as Æ ----- AE : ae : b Æ : b æ : IgnoreCase : -------- ae the same as Æ ----- AE : f l ae : f l Æ : f l æ : f l Original : Is U" or u" the same as Ü or ü? No options : -------- u" the same as Ü ----- U" : b u" : b Ü : b ü : b Ordinal : -------- u" the same as Ü ----- U" : u" : b Ü : b ü : IgnoreCase : -------- u" the same as Ü ----- U" : f l u" : f l Ü : f l ü : f l */
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.
Note