CompareInfo.LastIndexOf Method (String, Char, Int32, Int32, CompareOptions)
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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 using the specified CompareOptions value.
Namespace: System.Globalization
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
<SecuritySafeCriticalAttribute> _
Public Overridable Function LastIndexOf ( _
source As String, _
value As Char, _
startIndex As Integer, _
count As Integer, _
options As CompareOptions _
) As Integer
[SecuritySafeCriticalAttribute]
public virtual int LastIndexOf(
string source,
char value,
int startIndex,
int count,
CompareOptions options
)
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.
- options
Type: System.Globalization.CompareOptions
The CompareOptions value that defines how source and value should be compared. options is either the value Ordinal used by itself, or the bitwise combination of one or more of the following values: IgnoreCase, IgnoreSymbols, IgnoreNonSpace, IgnoreWidth, and IgnoreKanaType.
Return Value
Type: System.Int32
The 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 using the specified CompareOptions value, if found; otherwise, -1.
Exceptions
| Exception | Condition |
|---|---|
| ArgumentNullException | source is nulla null reference (Nothing in Visual Basic). |
| 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. |
| ArgumentException | options contains an invalid CompareOptions value. |
Remarks
The source string is searched backward starting at startIndex and ending at startIndex - count + 1.
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.
Examples
The following example determines the indexes of the first and last occurrences of a character or a substring within a portion of a string.
Imports System.Globalization
Public Class Example
Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
' Creates CompareInfo for the InvariantCulture.
Dim myComp As CompareInfo = CultureInfo.InvariantCulture.CompareInfo
' iS is the starting index of the substring.
Dim [iS] As Integer = 8
' iL is the length of the substring.
Dim iL As Integer = 18
' myT1 and myT2 are the strings used for padding.
Dim myT1 As New [String]("-"c, [iS])
Dim myT2 As [String]
' Searches for the ligature Æ.
Dim myStr As [String] = "Is AE or ae the same as Æ or æ?"
myT2 = New [String]("-"c, myStr.Length - [iS] - iL)
outputBlock.Text &= vbCrLf
outputBlock.Text += String.Format("Original : {0}", myStr) & vbCrLf
outputBlock.Text += String.Format("No options : {0}{1}{2}", myT1, myStr.Substring([iS], iL), myT2) & vbCrLf
PrintMarker(outputBlock, " AE : ", myComp.IndexOf(myStr, "AE", [iS], iL), myComp.LastIndexOf(myStr, "AE", [iS] + iL - 1, iL))
PrintMarker(outputBlock, " ae : ", myComp.IndexOf(myStr, "ae", [iS], iL), myComp.LastIndexOf(myStr, "ae", [iS] + iL - 1, iL))
PrintMarker(outputBlock, " Æ : ", myComp.IndexOf(myStr, "Æ"c, [iS], iL), myComp.LastIndexOf(myStr, "Æ"c, [iS] + iL - 1, iL))
PrintMarker(outputBlock, " æ : ", myComp.IndexOf(myStr, "æ"c, [iS], iL), myComp.LastIndexOf(myStr, "æ"c, [iS] + iL - 1, iL))
outputBlock.Text += String.Format("Ordinal : {0}{1}{2}", myT1, myStr.Substring([iS], iL), myT2) & vbCrLf
PrintMarker(outputBlock, " AE : ", myComp.IndexOf(myStr, "AE", [iS], iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "AE", [iS] + iL - 1, iL, CompareOptions.Ordinal))
PrintMarker(outputBlock, " ae : ", myComp.IndexOf(myStr, "ae", [iS], iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "ae", [iS] + iL - 1, iL, CompareOptions.Ordinal))
PrintMarker(outputBlock, " Æ : ", myComp.IndexOf(myStr, "Æ"c, [iS], iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "Æ"c, [iS] + iL - 1, iL, CompareOptions.Ordinal))
PrintMarker(outputBlock, " æ : ", myComp.IndexOf(myStr, "æ"c, [iS], iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "æ"c, [iS] + iL - 1, iL, CompareOptions.Ordinal))
outputBlock.Text += String.Format("IgnoreCase : {0}{1}{2}", myT1, myStr.Substring([iS], iL), myT2) & vbCrLf
PrintMarker(outputBlock, " AE : ", myComp.IndexOf(myStr, "AE", [iS], iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "AE", [iS] + iL - 1, iL, CompareOptions.IgnoreCase))
PrintMarker(outputBlock, " ae : ", myComp.IndexOf(myStr, "ae", [iS], iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "ae", [iS] + iL - 1, iL, CompareOptions.IgnoreCase))
PrintMarker(outputBlock, " Æ : ", myComp.IndexOf(myStr, "Æ"c, [iS], iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "Æ"c, [iS] + iL - 1, iL, CompareOptions.IgnoreCase))
PrintMarker(outputBlock, " æ : ", myComp.IndexOf(myStr, "æ"c, [iS], iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "æ"c, [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 " & ChrW(&H55) & ChrW(&H308) & " or " & ChrW(&H75) & ChrW(&H308) & " the same as " & ChrW(&HDC) & " or " & ChrW(&HFC) & "?"
myT2 = New [String]("-"c, myStr.Length - [iS] - iL)
outputBlock.Text &= vbCrLf
outputBlock.Text += String.Format("Original : {0}", myStr) & vbCrLf
outputBlock.Text += String.Format("No options : {0}{1}{2}", myT1, myStr.Substring([iS], iL), myT2) & vbCrLf
PrintMarker(outputBlock, " U" & ChrW(&H308) & " : ", myComp.IndexOf(myStr, "U" & ChrW(&H308), [iS], iL), myComp.LastIndexOf(myStr, "U" & ChrW(&H308), [iS] + iL - 1, iL))
PrintMarker(outputBlock, " u" & ChrW(&H308) & " : ", myComp.IndexOf(myStr, "u" & ChrW(&H308), [iS], iL), myComp.LastIndexOf(myStr, "u" & ChrW(&H308), [iS] + iL - 1, iL))
PrintMarker(outputBlock, " Ü : ", myComp.IndexOf(myStr, "Ü"c, [iS], iL), myComp.LastIndexOf(myStr, "Ü"c, [iS] + iL - 1, iL))
PrintMarker(outputBlock, " ü : ", myComp.IndexOf(myStr, "ü"c, [iS], iL), myComp.LastIndexOf(myStr, "ü"c, [iS] + iL - 1, iL))
outputBlock.Text += String.Format("Ordinal : {0}{1}{2}", myT1, myStr.Substring([iS], iL), myT2) & vbCrLf
PrintMarker(outputBlock, " U" & ChrW(&H308) & " : ", myComp.IndexOf(myStr, "U" & ChrW(&H308), [iS], iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "U" & ChrW(&H308), [iS] + iL - 1, iL, CompareOptions.Ordinal))
PrintMarker(outputBlock, " u" & ChrW(&H308) & " : ", myComp.IndexOf(myStr, "u" & ChrW(&H308), [iS], iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "u" & ChrW(&H308), [iS] + iL - 1, iL, CompareOptions.Ordinal))
PrintMarker(outputBlock, " Ü : ", myComp.IndexOf(myStr, "Ü"c, [iS], iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "Ü"c, [iS] + iL - 1, iL, CompareOptions.Ordinal))
PrintMarker(outputBlock, " ü : ", myComp.IndexOf(myStr, "ü"c, [iS], iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "ü"c, [iS] + iL - 1, iL, CompareOptions.Ordinal))
outputBlock.Text += String.Format("IgnoreCase : {0}{1}{2}", myT1, myStr.Substring([iS], iL), myT2) & vbCrLf
PrintMarker(outputBlock, " U" & ChrW(&H308) & " : ", myComp.IndexOf(myStr, "U" & ChrW(&H308), [iS], iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "U" & ChrW(&H308), [iS] + iL - 1, iL, CompareOptions.IgnoreCase))
PrintMarker(outputBlock, " u" & ChrW(&H308) & " : ", myComp.IndexOf(myStr, "u" & ChrW(&H308), [iS], iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "u" & ChrW(&H308), [iS] + iL - 1, iL, CompareOptions.IgnoreCase))
PrintMarker(outputBlock, " Ü : ", myComp.IndexOf(myStr, "Ü"c, [iS], iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "Ü"c, [iS] + iL - 1, iL, CompareOptions.IgnoreCase))
PrintMarker(outputBlock, " ü : ", myComp.IndexOf(myStr, "ü"c, [iS], iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "ü"c, [iS] + iL - 1, iL, CompareOptions.IgnoreCase))
End Sub 'Main
Public Shared Sub PrintMarker(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal Prefix As [String], ByVal First As Integer, ByVal Last As Integer)
' Determines the size of the array to create.
Dim mySize As Integer
If Last > First Then
mySize = Last
Else
mySize = First
End If
If mySize > -1 Then
' Creates an array of Char to hold the markers.
Dim myCharArr(mySize + 1) As [Char]
' Inserts the appropriate markers.
If First > -1 Then
myCharArr(First) = "f"c
End If
If Last > -1 Then
myCharArr(Last) = "l"c
End If
If First = Last Then
myCharArr(First) = "b"c
End If
' Displays the array of Char as a String.
outputBlock.Text += String.Format("{0}{1}", Prefix, New [String](myCharArr)) & vbCrLf
Else
outputBlock.Text &= Prefix & vbCrLf
End If
End Sub 'PrintMarker
End Class 'SamplesCompareInfo
'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
using System;
using System.Globalization;
public class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
// 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 = new String('-', iS);
String myT2;
// Searches for the ligature Æ.
String myStr = "Is AE or ae the same as Æ or æ?";
myT2 = new String('-', myStr.Length - iS - iL);
outputBlock.Text += "\n";
outputBlock.Text += String.Format("Original : {0}", myStr) + "\n";
outputBlock.Text += String.Format("No options : {0}{1}{2}", myT1, myStr.Substring(iS, iL), myT2) + "\n";
PrintMarker(outputBlock, " AE : ", myComp.IndexOf(myStr, "AE", iS, iL), myComp.LastIndexOf(myStr, "AE", iS + iL - 1, iL));
PrintMarker(outputBlock, " ae : ", myComp.IndexOf(myStr, "ae", iS, iL), myComp.LastIndexOf(myStr, "ae", iS + iL - 1, iL));
PrintMarker(outputBlock, " Æ : ", myComp.IndexOf(myStr, 'Æ', iS, iL), myComp.LastIndexOf(myStr, 'Æ', iS + iL - 1, iL));
PrintMarker(outputBlock, " æ : ", myComp.IndexOf(myStr, 'æ', iS, iL), myComp.LastIndexOf(myStr, 'æ', iS + iL - 1, iL));
outputBlock.Text += String.Format("Ordinal : {0}{1}{2}", myT1, myStr.Substring(iS, iL), myT2) + "\n";
PrintMarker(outputBlock, " AE : ", myComp.IndexOf(myStr, "AE", iS, iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "AE", iS + iL - 1, iL, CompareOptions.Ordinal));
PrintMarker(outputBlock, " ae : ", myComp.IndexOf(myStr, "ae", iS, iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "ae", iS + iL - 1, iL, CompareOptions.Ordinal));
PrintMarker(outputBlock, " Æ : ", myComp.IndexOf(myStr, 'Æ', iS, iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, 'Æ', iS + iL - 1, iL, CompareOptions.Ordinal));
PrintMarker(outputBlock, " æ : ", myComp.IndexOf(myStr, 'æ', iS, iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, 'æ', iS + iL - 1, iL, CompareOptions.Ordinal));
outputBlock.Text += String.Format("IgnoreCase : {0}{1}{2}", myT1, myStr.Substring(iS, iL), myT2) + "\n";
PrintMarker(outputBlock, " AE : ", myComp.IndexOf(myStr, "AE", iS, iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "AE", iS + iL - 1, iL, CompareOptions.IgnoreCase));
PrintMarker(outputBlock, " ae : ", myComp.IndexOf(myStr, "ae", iS, iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "ae", iS + iL - 1, iL, CompareOptions.IgnoreCase));
PrintMarker(outputBlock, " Æ : ", myComp.IndexOf(myStr, 'Æ', iS, iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, 'Æ', iS + iL - 1, iL, CompareOptions.IgnoreCase));
PrintMarker(outputBlock, " æ : ", myComp.IndexOf(myStr, 'æ', iS, iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, '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 \u0055\u0308 or \u0075\u0308 the same as \u00DC or \u00FC?";
myT2 = new String('-', myStr.Length - iS - iL);
outputBlock.Text += "\n";
outputBlock.Text += String.Format("Original : {0}", myStr) + "\n";
outputBlock.Text += String.Format("No options : {0}{1}{2}", myT1, myStr.Substring(iS, iL), myT2) + "\n";
PrintMarker(outputBlock, " U\u0308 : ", myComp.IndexOf(myStr, "U\u0308", iS, iL), myComp.LastIndexOf(myStr, "U\u0308", iS + iL - 1, iL));
PrintMarker(outputBlock, " u\u0308 : ", myComp.IndexOf(myStr, "u\u0308", iS, iL), myComp.LastIndexOf(myStr, "u\u0308", iS + iL - 1, iL));
PrintMarker(outputBlock, " Ü : ", myComp.IndexOf(myStr, 'Ü', iS, iL), myComp.LastIndexOf(myStr, 'Ü', iS + iL - 1, iL));
PrintMarker(outputBlock, " ü : ", myComp.IndexOf(myStr, 'ü', iS, iL), myComp.LastIndexOf(myStr, 'ü', iS + iL - 1, iL));
outputBlock.Text += String.Format("Ordinal : {0}{1}{2}", myT1, myStr.Substring(iS, iL), myT2) + "\n";
PrintMarker(outputBlock, " U\u0308 : ", myComp.IndexOf(myStr, "U\u0308", iS, iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "U\u0308", iS + iL - 1, iL, CompareOptions.Ordinal));
PrintMarker(outputBlock, " u\u0308 : ", myComp.IndexOf(myStr, "u\u0308", iS, iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "u\u0308", iS + iL - 1, iL, CompareOptions.Ordinal));
PrintMarker(outputBlock, " Ü : ", myComp.IndexOf(myStr, 'Ü', iS, iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, 'Ü', iS + iL - 1, iL, CompareOptions.Ordinal));
PrintMarker(outputBlock, " ü : ", myComp.IndexOf(myStr, 'ü', iS, iL, CompareOptions.Ordinal), myComp.LastIndexOf(myStr, 'ü', iS + iL - 1, iL, CompareOptions.Ordinal));
outputBlock.Text += String.Format("IgnoreCase : {0}{1}{2}", myT1, myStr.Substring(iS, iL), myT2) + "\n";
PrintMarker(outputBlock, " U\u0308 : ", myComp.IndexOf(myStr, "U\u0308", iS, iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "U\u0308", iS + iL - 1, iL, CompareOptions.IgnoreCase));
PrintMarker(outputBlock, " u\u0308 : ", myComp.IndexOf(myStr, "u\u0308", iS, iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "u\u0308", iS + iL - 1, iL, CompareOptions.IgnoreCase));
PrintMarker(outputBlock, " Ü : ", myComp.IndexOf(myStr, 'Ü', iS, iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, 'Ü', iS + iL - 1, iL, CompareOptions.IgnoreCase));
PrintMarker(outputBlock, " ü : ", myComp.IndexOf(myStr, 'ü', iS, iL, CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, 'ü', iS + iL - 1, iL, CompareOptions.IgnoreCase));
}
public static void PrintMarker(System.Windows.Controls.TextBlock outputBlock, 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.
outputBlock.Text += String.Format("{0}{1}", Prefix, new String(myCharArr)) + "\n";
}
else
outputBlock.Text += Prefix + "\n";
}
}
/*
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
*/
Version Information
Silverlight
Supported in: 5, 4, 3
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0
XNA Framework
Supported in: Xbox 360, Windows Phone OS 7.0
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.
See Also