CompareInfo.LastIndexOf Method (String, Char, Int32, Int32)
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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.
Namespace: System.Globalization
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Overridable Function LastIndexOf ( _
source As String, _
value As Char, _
startIndex As Integer, _
count As Integer _
) As Integer
public virtual int LastIndexOf(
string source,
char 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.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, 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. |
Remarks
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.
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.