CompareInfo.LastIndexOf Method (String, Char, Int32, CompareOptions)
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Searches for the specified character and returns the zero-based index of the last occurrence within the section of the source string that extends from the beginning of the string to the specified index using the specified CompareOptions value.
Assembly: mscorlib (in mscorlib.dll)
'Declaration Public Overridable Function LastIndexOf ( _ source As String, _ value As Char, _ startIndex As Integer, _ options As CompareOptions _ ) As Integer
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.
- 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.Int32The zero-based index of the last occurrence of value within the section of source that extends from the beginning of source to startIndex using the specified CompareOptions value, if found; otherwise, -1.
| Exception | Condition |
|---|---|
| ArgumentNullException | source is Nothing. |
| ArgumentOutOfRangeException | startIndex is outside the range of valid indexes for source. |
| ArgumentException | options contains an invalid CompareOptions value. |
The source string is searched backward starting at startIndex 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.
The following 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.
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 = 20 ' myT1 is the string used for padding. Dim myT1 As [String] ' Searches for the ligature Æ. Dim myStr As [String] = "Is AE or ae the same as Æ or æ?" outputBlock.Text &= vbCrLf myT1 = New [String]("-"c, [iS]) outputBlock.Text += String.Format("IndexOf( String, *, {0}, * )", [iS]) & vbCrLf outputBlock.Text += String.Format("Original : {0}", myStr) & vbCrLf outputBlock.Text += String.Format("No options : {0}{1}", myT1, myStr.Substring([iS])) & vbCrLf PrintMarker(outputBlock, " AE : ", myComp.IndexOf(myStr, "AE", [iS], CompareOptions.None), -1) PrintMarker(outputBlock, " ae : ", myComp.IndexOf(myStr, "ae", [iS], CompareOptions.None), -1) PrintMarker(outputBlock, " Æ : ", myComp.IndexOf(myStr, "Æ"c, [iS], CompareOptions.None), -1) PrintMarker(outputBlock, " æ : ", myComp.IndexOf(myStr, "æ"c, [iS], CompareOptions.None), -1) outputBlock.Text += String.Format("Ordinal : {0}{1}", myT1, myStr.Substring([iS])) & vbCrLf PrintMarker(outputBlock, " AE : ", myComp.IndexOf(myStr, "AE", [iS], CompareOptions.Ordinal), -1) PrintMarker(outputBlock, " ae : ", myComp.IndexOf(myStr, "ae", [iS], CompareOptions.Ordinal), -1) PrintMarker(outputBlock, " Æ : ", myComp.IndexOf(myStr, "Æ"c, [iS], CompareOptions.Ordinal), -1) PrintMarker(outputBlock, " æ : ", myComp.IndexOf(myStr, "æ"c, [iS], CompareOptions.Ordinal), -1) outputBlock.Text += String.Format("IgnoreCase : {0}{1}", myT1, myStr.Substring([iS])) & vbCrLf PrintMarker(outputBlock, " AE : ", myComp.IndexOf(myStr, "AE", [iS], CompareOptions.IgnoreCase), -1) PrintMarker(outputBlock, " ae : ", myComp.IndexOf(myStr, "ae", [iS], CompareOptions.IgnoreCase), -1) PrintMarker(outputBlock, " Æ : ", myComp.IndexOf(myStr, "Æ"c, [iS], CompareOptions.IgnoreCase), -1) PrintMarker(outputBlock, " æ : ", myComp.IndexOf(myStr, "æ"c, [iS], CompareOptions.IgnoreCase), -1) myT1 = New [String]("-"c, myStr.Length - [iS] - 1) outputBlock.Text += String.Format("LastIndexOf( String, *, {0}, * )", [iS]) & vbCrLf outputBlock.Text += String.Format("Original : {0}", myStr) & vbCrLf outputBlock.Text += String.Format("No options : {0}{1}", myStr.Substring(0, [iS] + 1), myT1) & vbCrLf PrintMarker(outputBlock, " AE : ", -1, myComp.LastIndexOf(myStr, "AE", [iS], CompareOptions.None)) PrintMarker(outputBlock, " ae : ", -1, myComp.LastIndexOf(myStr, "ae", [iS], CompareOptions.None)) PrintMarker(outputBlock, " Æ : ", -1, myComp.LastIndexOf(myStr, "Æ"c, [iS], CompareOptions.None)) PrintMarker(outputBlock, " æ : ", -1, myComp.LastIndexOf(myStr, "æ"c, [iS], CompareOptions.None)) outputBlock.Text += String.Format("Ordinal : {0}{1}", myStr.Substring(0, [iS] + 1), myT1) & vbCrLf PrintMarker(outputBlock, " AE : ", -1, myComp.LastIndexOf(myStr, "AE", [iS], CompareOptions.Ordinal)) PrintMarker(outputBlock, " ae : ", -1, myComp.LastIndexOf(myStr, "ae", [iS], CompareOptions.Ordinal)) PrintMarker(outputBlock, " Æ : ", -1, myComp.LastIndexOf(myStr, "Æ"c, [iS], CompareOptions.Ordinal)) PrintMarker(outputBlock, " æ : ", -1, myComp.LastIndexOf(myStr, "æ"c, [iS], CompareOptions.Ordinal)) outputBlock.Text += String.Format("IgnoreCase : {0}{1}", myStr.Substring(0, [iS] + 1), myT1) & vbCrLf PrintMarker(outputBlock, " AE : ", -1, myComp.LastIndexOf(myStr, "AE", [iS], CompareOptions.IgnoreCase)) PrintMarker(outputBlock, " ae : ", -1, myComp.LastIndexOf(myStr, "ae", [iS], CompareOptions.IgnoreCase)) PrintMarker(outputBlock, " Æ : ", -1, myComp.LastIndexOf(myStr, "Æ"c, [iS], CompareOptions.IgnoreCase)) PrintMarker(outputBlock, " æ : ", -1, myComp.LastIndexOf(myStr, "æ"c, [iS], 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) & "?" outputBlock.Text &= vbCrLf myT1 = New [String]("-"c, [iS]) outputBlock.Text += String.Format("IndexOf( String, *, {0}, * )", [iS]) & vbCrLf outputBlock.Text += String.Format("Original : {0}", myStr) & vbCrLf outputBlock.Text += String.Format("No options : {0}{1}", myT1, myStr.Substring([iS])) & vbCrLf PrintMarker(outputBlock, " U" & ChrW(&H308) & " : ", myComp.IndexOf(myStr, "U" & ChrW(&H308), [iS], CompareOptions.None), -1) PrintMarker(outputBlock, " u" & ChrW(&H308) & " : ", myComp.IndexOf(myStr, "u" & ChrW(&H308), [iS], CompareOptions.None), -1) PrintMarker(outputBlock, " Ü : ", myComp.IndexOf(myStr, "Ü"c, [iS], CompareOptions.None), -1) PrintMarker(outputBlock, " ü : ", myComp.IndexOf(myStr, "ü"c, [iS], CompareOptions.None), -1) outputBlock.Text += String.Format("Ordinal : {0}{1}", myT1, myStr.Substring([iS])) & vbCrLf PrintMarker(outputBlock, " U" & ChrW(&H308) & " : ", myComp.IndexOf(myStr, "U" & ChrW(&H308), [iS], CompareOptions.Ordinal), -1) PrintMarker(outputBlock, " u" & ChrW(&H308) & " : ", myComp.IndexOf(myStr, "u" & ChrW(&H308), [iS], CompareOptions.Ordinal), -1) PrintMarker(outputBlock, " Ü : ", myComp.IndexOf(myStr, "Ü"c, [iS], CompareOptions.Ordinal), -1) PrintMarker(outputBlock, " ü : ", myComp.IndexOf(myStr, "ü"c, [iS], CompareOptions.Ordinal), -1) outputBlock.Text += String.Format("IgnoreCase : {0}{1}", myT1, myStr.Substring([iS])) & vbCrLf PrintMarker(outputBlock, " U" & ChrW(&H308) & " : ", myComp.IndexOf(myStr, "U" & ChrW(&H308), [iS], CompareOptions.IgnoreCase), -1) PrintMarker(outputBlock, " u" & ChrW(&H308) & " : ", myComp.IndexOf(myStr, "u" & ChrW(&H308), [iS], CompareOptions.IgnoreCase), -1) PrintMarker(outputBlock, " Ü : ", myComp.IndexOf(myStr, "Ü"c, [iS], CompareOptions.IgnoreCase), -1) PrintMarker(outputBlock, " ü : ", myComp.IndexOf(myStr, "ü"c, [iS], CompareOptions.IgnoreCase), -1) myT1 = New [String]("-"c, myStr.Length - [iS] - 1) outputBlock.Text += String.Format("LastIndexOf( String, *, {0}, * )", [iS]) & vbCrLf outputBlock.Text += String.Format("Original : {0}", myStr) & vbCrLf outputBlock.Text += String.Format("No options : {0}{1}", myStr.Substring(0, [iS] + 1), myT1) & vbCrLf PrintMarker(outputBlock, " U" & ChrW(&H308) & " : ", -1, myComp.LastIndexOf(myStr, "U" & ChrW(&H308), [iS], CompareOptions.None)) PrintMarker(outputBlock, " u" & ChrW(&H308) & " : ", -1, myComp.LastIndexOf(myStr, "u" & ChrW(&H308), [iS], CompareOptions.None)) PrintMarker(outputBlock, " Ü : ", -1, myComp.LastIndexOf(myStr, "Ü"c, [iS], CompareOptions.None)) PrintMarker(outputBlock, " ü : ", -1, myComp.LastIndexOf(myStr, "ü"c, [iS], CompareOptions.None)) outputBlock.Text += String.Format("Ordinal : {0}{1}", myStr.Substring(0, [iS] + 1), myT1) & vbCrLf PrintMarker(outputBlock, " U" & ChrW(&H308) & " : ", -1, myComp.LastIndexOf(myStr, "U" & ChrW(&H308), [iS], CompareOptions.Ordinal)) PrintMarker(outputBlock, " u" & ChrW(&H308) & " : ", -1, myComp.LastIndexOf(myStr, "u" & ChrW(&H308), [iS], CompareOptions.Ordinal)) PrintMarker(outputBlock, " Ü : ", -1, myComp.LastIndexOf(myStr, "Ü"c, [iS], CompareOptions.Ordinal)) PrintMarker(outputBlock, " ü : ", -1, myComp.LastIndexOf(myStr, "ü"c, [iS], CompareOptions.Ordinal)) outputBlock.Text += String.Format("IgnoreCase : {0}{1}", myStr.Substring(0, [iS] + 1), myT1) & vbCrLf PrintMarker(outputBlock, " U" & ChrW(&H308) & " : ", -1, myComp.LastIndexOf(myStr, "U" & ChrW(&H308), [iS], CompareOptions.IgnoreCase)) PrintMarker(outputBlock, " u" & ChrW(&H308) & " : ", -1, myComp.LastIndexOf(myStr, "u" & ChrW(&H308), [iS], CompareOptions.IgnoreCase)) PrintMarker(outputBlock, " Ü : ", -1, myComp.LastIndexOf(myStr, "Ü"c, [iS], CompareOptions.IgnoreCase)) PrintMarker(outputBlock, " ü : ", -1, myComp.LastIndexOf(myStr, "ü"c, [iS], 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. ' '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