CompareInfo::LastIndexOf Method (String^, Char, CompareOptions)
Searches for the specified character and returns the zero-based index of the last occurrence within the entire source string using the specified CompareOptions value.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- source
-
Type:
System::String^
The string to search.
- value
-
Type:
System::Char
The character to locate within source.
- options
-
Type:
System.Globalization::CompareOptions
A value that defines how source and value should be compared. options is either the enumeration value Ordinal, or a bitwise combination of one or more of the following values: IgnoreCase, IgnoreSymbols, IgnoreNonSpace, IgnoreWidth, and IgnoreKanaType.
Return Value
Type: System::Int32The zero-based index of the last occurrence of value, if found, within source, using the specified comparison options; otherwise, -1.
| Exception | Condition |
|---|---|
| ArgumentNullException | source is null. |
| ArgumentException | options contains an invalid CompareOptions value. |
The source string is searched backward starting at the end of the string and ending at the beginning of the string.
The CompareOptions::StringSort value is not valid for this method.
If options does not include the Ordinal value, 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. If options includes the Ordinal value, this overload performs an ordinal (culture-insensitive) search. A character is considered equivalent to another character only if the Unicode values are the same. Overloads of String::LastIndexOf that search for a character perform an ordinal search, whereas those that search for a string perform a culture-sensitive search.
Note |
|---|
When possible, you should call string comparison methods that have a parameter of type CompareOptions to specify the kind of comparison expected. As a general rule, use linguistic options (using the current culture) for comparing strings displayed in the user interface and specify CompareOptions::Ordinal or CompareOptions::OrdinalIgnoreCase for security comparisons. |
Notes to Callers:
Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive sort. In a culture-sensitive search, if value is an ignorable character, the result is equivalent to searching with that character removed. In this case, the LastIndexOf(String^, Char, CompareOptions) method always returns the last character position in source to indicate that the match is found at the end of source. In the following example, the LastIndexOf(String^, Char, CompareOptions) method is used to search for a soft hyphen (U+00AD) in two strings. Only one of the strings contains a soft hyphen. In both cases, because the soft hyphen is an ignorable character, a culture-sensitive search returns the last index position in the source string. In contrast, an ordinal search successfully finds the soft hyphen in one string and reports that it is absent from the second string.
The following example determines the indexes of the first and last occurrences of a character or a substring within 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; // Searches for the ligature Æ. String^ myStr = "Is AE or ae the same as Æ or æ?"; Console::WriteLine(); Console::WriteLine( "No options : {0}", myStr ); PrintMarker( " AE : ", myComp->IndexOf( myStr, "AE" ), myComp->LastIndexOf( myStr, "AE" ) ); PrintMarker( " ae : ", myComp->IndexOf( myStr, "ae" ), myComp->LastIndexOf( myStr, "ae" ) ); PrintMarker( " Æ : ", myComp->IndexOf( myStr, L'Æ' ), myComp->LastIndexOf( myStr, L'Æ' ) ); PrintMarker( " æ : ", myComp->IndexOf( myStr, L'æ' ), myComp->LastIndexOf( myStr, L'æ' ) ); Console::WriteLine( "Ordinal : {0}", myStr ); PrintMarker( " AE : ", myComp->IndexOf( myStr, "AE", CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, "AE", CompareOptions::Ordinal ) ); PrintMarker( " ae : ", myComp->IndexOf( myStr, "ae", CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, "ae", CompareOptions::Ordinal ) ); PrintMarker( " Æ : ", myComp->IndexOf( myStr, L'Æ', CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, L'Æ', CompareOptions::Ordinal ) ); PrintMarker( " æ : ", myComp->IndexOf( myStr, L'æ', CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, L'æ', CompareOptions::Ordinal ) ); Console::WriteLine( "IgnoreCase : {0}", myStr ); PrintMarker( " AE : ", myComp->IndexOf( myStr, "AE", CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, "AE", CompareOptions::IgnoreCase ) ); PrintMarker( " ae : ", myComp->IndexOf( myStr, "ae", CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, "ae", CompareOptions::IgnoreCase ) ); PrintMarker( " Æ : ", myComp->IndexOf( myStr, L'Æ', CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, L'Æ', CompareOptions::IgnoreCase ) ); PrintMarker( " æ : ", myComp->IndexOf( myStr, L'æ', CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, L'æ', 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?"; Console::WriteLine(); Console::WriteLine( "No options : {0}", myStr ); PrintMarker( " U\u0308 : ", myComp->IndexOf( myStr, "U\u0308" ), myComp->LastIndexOf( myStr, "U\u0308" ) ); PrintMarker( " u\u0308 : ", myComp->IndexOf( myStr, "u\u0308" ), myComp->LastIndexOf( myStr, "u\u0308" ) ); PrintMarker( " Ü : ", myComp->IndexOf( myStr, L'Ü' ), myComp->LastIndexOf( myStr, L'Ü' ) ); PrintMarker( " ü : ", myComp->IndexOf( myStr, L'ü' ), myComp->LastIndexOf( myStr, L'ü' ) ); Console::WriteLine( "Ordinal : {0}", myStr ); PrintMarker( " U\u0308 : ", myComp->IndexOf( myStr, "U\u0308", CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, "U\u0308", CompareOptions::Ordinal ) ); PrintMarker( " u\u0308 : ", myComp->IndexOf( myStr, "u\u0308", CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, "u\u0308", CompareOptions::Ordinal ) ); PrintMarker( " Ü : ", myComp->IndexOf( myStr, L'Ü', CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, L'Ü', CompareOptions::Ordinal ) ); PrintMarker( " ü : ", myComp->IndexOf( myStr, L'ü', CompareOptions::Ordinal ), myComp->LastIndexOf( myStr, L'ü', CompareOptions::Ordinal ) ); Console::WriteLine( "IgnoreCase : {0}", myStr ); PrintMarker( " U\u0308 : ", myComp->IndexOf( myStr, "U\u0308", CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, "U\u0308", CompareOptions::IgnoreCase ) ); PrintMarker( " u\u0308 : ", myComp->IndexOf( myStr, "u\u0308", CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, "u\u0308", CompareOptions::IgnoreCase ) ); PrintMarker( " Ü : ", myComp->IndexOf( myStr, L'Ü', CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, L'Ü', CompareOptions::IgnoreCase ) ); PrintMarker( " ü : ", myComp->IndexOf( myStr, L'ü', CompareOptions::IgnoreCase ), myComp->LastIndexOf( myStr, L'ü', CompareOptions::IgnoreCase ) ); } /* This code produces the following output. No options : Is AE or ae the same as Æ or æ? AE : f l ae : f l Æ : f l æ : f l Ordinal : Is AE or ae the same as Æ or æ? AE : b ae : b Æ : b æ : b IgnoreCase : Is AE or ae the same as Æ or æ? AE : f l ae : f l Æ : f l æ : f l No options : Is U" or u" the same as Ü or ü? U" : f l u" : f l Ü : f l ü : f l Ordinal : Is U" or u" the same as Ü or ü? U" : b u" : b Ü : b ü : b IgnoreCase : Is U" or u" the same as Ü or ü? U" : f l u" : f l Ü : f l ü : f l */
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
