Reports the zero-based index position of the last occurrence of a specified string within this instance. The search starts at a specified character position and proceeds backward toward the beginning of the string for the specified number of character positions. A parameter specifies the type of comparison to perform when searching for the specified string.
Assembly: mscorlib (in mscorlib.dll)
Public Function LastIndexOf ( _
value As [%$TOPIC/ms224421_en-us_VS_110_1_0_0_0_0%], _
startIndex As [%$TOPIC/ms224421_en-us_VS_110_1_0_0_0_1%], _
count As [%$TOPIC/ms224421_en-us_VS_110_1_0_0_0_2%], _
comparisonType As [%$TOPIC/ms224421_en-us_VS_110_1_0_0_0_3%] _
) As [%$TOPIC/ms224421_en-us_VS_110_1_0_0_0_4%]public [%$TOPIC/ms224421_en-us_VS_110_1_0_1_0_0%] LastIndexOf(
[%$TOPIC/ms224421_en-us_VS_110_1_0_1_0_1%] value,
[%$TOPIC/ms224421_en-us_VS_110_1_0_1_0_2%] startIndex,
[%$TOPIC/ms224421_en-us_VS_110_1_0_1_0_3%] count,
[%$TOPIC/ms224421_en-us_VS_110_1_0_1_0_4%] comparisonType
)public:
[%$TOPIC/ms224421_en-us_VS_110_1_0_2_0_0%] LastIndexOf(
[%$TOPIC/ms224421_en-us_VS_110_1_0_2_0_1%]^ value,
[%$TOPIC/ms224421_en-us_VS_110_1_0_2_0_2%] startIndex,
[%$TOPIC/ms224421_en-us_VS_110_1_0_2_0_3%] count,
[%$TOPIC/ms224421_en-us_VS_110_1_0_2_0_4%] comparisonType
)member LastIndexOf :
value:[%$TOPIC/ms224421_en-us_VS_110_1_0_3_0_0%] *
startIndex:[%$TOPIC/ms224421_en-us_VS_110_1_0_3_0_1%] *
count:[%$TOPIC/ms224421_en-us_VS_110_1_0_3_0_2%] *
comparisonType:[%$TOPIC/ms224421_en-us_VS_110_1_0_3_0_3%] -> [%$TOPIC/ms224421_en-us_VS_110_1_0_3_0_4%]Parameters
- value
- Type:
SystemString
The string to seek.
- startIndex
- Type:
SystemInt32
The search starting position. The search proceeds from startIndex toward the beginning of this instance.
- count
- Type:
SystemInt32
The number of character positions to examine.
- comparisonType
- Type:
SystemStringComparison
One of the enumeration values that specifies the rules for the search.
Return Value
Type: SystemInt32The index position of the value parameter if that string is found, or -1 if it is not found or if the current instance equals StringEmpty. If value is StringEmpty, the return value is the smaller of startIndex and the last index position in this instance.
| Exception | Condition |
|---|---|
| ArgumentNullException | value is . |
| ArgumentOutOfRangeException | count is negative. -or- The current instance does not equal StringEmpty, and startIndex is negative. -or- The current instance does not equal StringEmpty, and startIndex is greater than the length of this instance. -or- The current instance does not equal StringEmpty, and startIndex + 1 - count specifies a position that is not within this instance. |
| ArgumentException | comparisonType is not a valid SystemStringComparison value. |
Index numbering starts from zero. That is, the first character in the string is at index zero and the last is at Length - 1.
The search begins at the startIndex character position and proceeds backward until either value is found or count character positions have been examined. For example, if startIndex is Length - 1, the method searches backward count characters from the last character in the string.
The comparisonType parameter specifies to search for the value parameter using the current or invariant culture, using a case-sensitive or case-insensitive search, and using word or ordinal comparison rules.
Notes to CallersCharacter sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. In a culture-sensitive search (that is, if comparisonType is not StringComparisonOrdinal or StringComparisonOrdinalIgnoreCase), if value contains an ignorable character, the result is equivalent to searching with that character removed. If value consists only of one or more ignorable characters, the LastIndexOf(String, Int32, Int32, StringComparison) method always returns startIndex, which is the character position at which the search begins.
In the following example, the LastIndexOf(String, Int32, Int32, StringComparison) method is used to find the position of a soft hyphen (U+00AD) followed by an "m" in all but the first character position before the final "m" in two strings. Only one of the strings contains the required substring. In both cases, because the soft hyphen is an ignorable character, the method returns the index of "m" in the string when it performs a culture-sensitive comparison. When it performs an ordinal comparison, however, it finds the substring only in the first string. Note that in the case of the first string, which includes the soft hyphen followed by an "m", the method fails to return the index of the soft hyphen but instead returns the index of the "m" when it performs a culture-sensitive comparison. The method returns the index of the soft hyphen in the first string only when it performs an ordinal comparison.
Public Module Example
Public Sub Main()
Dim searchString As String = ChrW(&h00AD) + "m"
Dim s1 As String = "ani" + ChrW(&h00AD) + "m"
Dim s2 As String = "animal"
Dim position As Integer
position = s1.LastIndexOf("m"c)
If position >= 1 Then
Console.WriteLine(s1.LastIndexOf(searchString, position, position, StringComparison.CurrentCulture))
Console.WriteLine(s1.LastIndexOf(searchString, position, position, StringComparison.Ordinal))
End If
position = s2.LastIndexOf("m"c)
If position >= 1 Then
Console.WriteLine(s2.LastIndexOf(searchString, position, position, StringComparison.CurrentCulture))
Console.WriteLine(s2.LastIndexOf(searchString, position, position, StringComparison.Ordinal))
End If
End Sub
End Module
' The example displays the following output:
' 4
' 3
' 3
' -1using System;
public class Example
{
public static void Main()
{
string searchString = "\u00ADm";
string s1 = "ani\u00ADmal" ;
string s2 = "animal";
int position;
position = s1.LastIndexOf('m');
if (position >= 1) {
Console.WriteLine(s1.LastIndexOf(searchString, position, position, StringComparison.CurrentCulture));
Console.WriteLine(s1.LastIndexOf(searchString, position, position, StringComparison.Ordinal));
}
position = s2.LastIndexOf('m');
if (position >= 1) {
Console.WriteLine(s2.LastIndexOf(searchString, position, position, StringComparison.CurrentCulture));
Console.WriteLine(s2.LastIndexOf(searchString, position, position, StringComparison.Ordinal));
}
}
}
// The example displays the following output:
// 4
// 3
// 3
// -1The following example demonstrates three overloads of the LastIndexOf method that find the last occurrence of a string within another string using different values of the StringComparison enumeration.
' This code example demonstrates the
' System.String.LastIndexOf(String, ..., StringComparison) methods.
Imports System
Imports System.Threading
Imports System.Globalization
Class Sample
Public Shared Sub Main()
Dim intro As String = "Find the last occurrence of a character using different " & _
"values of StringComparison."
Dim resultFmt As String = "Comparison: {0,-28} Location: {1,3}"
' Define a string to search for.
' U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
Dim CapitalAWithRing As String = "Å"
' Define a string to search.
' The result of combining the characters LATIN SMALL LETTER A and COMBINING
' RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character
' LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
Dim cat As String = "A Cheshire c" & "å" & "t"
Dim loc As Integer = 0
Dim scValues As StringComparison() = { _
StringComparison.CurrentCulture, _
StringComparison.CurrentCultureIgnoreCase, _
StringComparison.InvariantCulture, _
StringComparison.InvariantCultureIgnoreCase, _
StringComparison.Ordinal, _
StringComparison.OrdinalIgnoreCase }
Dim sc As StringComparison
' Clear the screen and display an introduction.
Console.Clear()
Console.WriteLine(intro)
' Display the current culture because culture affects the result. For example,
' try this code example with the "sv-SE" (Swedish-Sweden) culture.
Thread.CurrentThread.CurrentCulture = New CultureInfo("en-US")
Console.WriteLine("The current culture is ""{0}"" - {1}.", _
Thread.CurrentThread.CurrentCulture.Name, _
Thread.CurrentThread.CurrentCulture.DisplayName)
' Display the string to search for and the string to search.
Console.WriteLine("Search for the string ""{0}"" in the string ""{1}""", _
CapitalAWithRing, cat)
Console.WriteLine()
' Note that in each of the following searches, we look for
' LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains
' LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates
' the string was not found.
' Search using different values of StringComparsion. Specify the start
' index and count.
Console.WriteLine("Part 1: Start index and count are specified.")
For Each sc In scValues
loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, cat.Length, sc)
Console.WriteLine(resultFmt, sc, loc)
Next sc
' Search using different values of StringComparsion. Specify the
' start index.
Console.WriteLine(vbCrLf & "Part 2: Start index is specified.")
For Each sc In scValues
loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, sc)
Console.WriteLine(resultFmt, sc, loc)
Next sc
' Search using different values of StringComparsion.
Console.WriteLine(vbCrLf & "Part 3: Neither start index nor count is specified.")
For Each sc In scValues
loc = cat.LastIndexOf(CapitalAWithRing, sc)
Console.WriteLine(resultFmt, sc, loc)
Next sc
End Sub 'Main
End Class 'Sample
'
'Note: This code example was executed on a console whose user interface
'culture is "en-US" (English-United States).
'
'This code example produces the following results:
'
'Find the last occurrence of a character using different values of StringComparison.
'The current culture is "en-US" - English (United States).
'Search for the string "Å" in the string "A Cheshire ca°t"
'
'Part 1: Start index and count are specified.
'Comparison: CurrentCulture Location: -1
'Comparison: CurrentCultureIgnoreCase Location: 12
'Comparison: InvariantCulture Location: -1
'Comparison: InvariantCultureIgnoreCase Location: 12
'Comparison: Ordinal Location: -1
'Comparison: OrdinalIgnoreCase Location: -1
'
'Part 2: Start index is specified.
'Comparison: CurrentCulture Location: -1
'Comparison: CurrentCultureIgnoreCase Location: 12
'Comparison: InvariantCulture Location: -1
'Comparison: InvariantCultureIgnoreCase Location: 12
'Comparison: Ordinal Location: -1
'Comparison: OrdinalIgnoreCase Location: -1
'
'Part 3: Neither start index nor count is specified.
'Comparison: CurrentCulture Location: -1
'Comparison: CurrentCultureIgnoreCase Location: 12
'Comparison: InvariantCulture Location: -1
'Comparison: InvariantCultureIgnoreCase Location: 12
'Comparison: Ordinal Location: -1
'Comparison: OrdinalIgnoreCase Location: -1
'// This code example demonstrates the
// System.String.LastIndexOf(String, ..., StringComparison) methods.
using System;
using System.Threading;
using System.Globalization;
class Sample
{
public static void Main()
{
string intro = "Find the last occurrence of a character using different " +
"values of StringComparison.";
string resultFmt = "Comparison: {0,-28} Location: {1,3}";
// Define a string to search for.
// U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
string CapitalAWithRing = "\u00c5";
// Define a string to search.
// The result of combining the characters LATIN SMALL LETTER A and COMBINING
// RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character
// LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
string cat = "A Cheshire c" + "\u0061\u030a" + "t";
int loc = 0;
StringComparison[] scValues = {
StringComparison.CurrentCulture,
StringComparison.CurrentCultureIgnoreCase,
StringComparison.InvariantCulture,
StringComparison.InvariantCultureIgnoreCase,
StringComparison.Ordinal,
StringComparison.OrdinalIgnoreCase };
// Clear the screen and display an introduction.
Console.Clear();
Console.WriteLine(intro);
// Display the current culture because culture affects the result. For example,
// try this code example with the "sv-SE" (Swedish-Sweden) culture.
Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
Console.WriteLine("The current culture is \"{0}\" - {1}.",
Thread.CurrentThread.CurrentCulture.Name,
Thread.CurrentThread.CurrentCulture.DisplayName);
// Display the string to search for and the string to search.
Console.WriteLine("Search for the string \"{0}\" in the string \"{1}\"",
CapitalAWithRing, cat);
Console.WriteLine();
// Note that in each of the following searches, we look for
// LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains
// LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates
// the string was not found.
// Search using different values of StringComparsion. Specify the start
// index and count.
Console.WriteLine("Part 1: Start index and count are specified.");
foreach (StringComparison sc in scValues)
{
loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, cat.Length, sc);
Console.WriteLine(resultFmt, sc, loc);
}
// Search using different values of StringComparsion. Specify the
// start index.
Console.WriteLine("\nPart 2: Start index is specified.");
foreach (StringComparison sc in scValues)
{
loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, sc);
Console.WriteLine(resultFmt, sc, loc);
}
// Search using different values of StringComparsion.
Console.WriteLine("\nPart 3: Neither start index nor count is specified.");
foreach (StringComparison sc in scValues)
{
loc = cat.LastIndexOf(CapitalAWithRing, sc);
Console.WriteLine(resultFmt, sc, loc);
}
}
}
/*
Note: This code example was executed on a console whose user interface
culture is "en-US" (English-United States).
This code example produces the following results:
Find the last occurrence of a character using different values of StringComparison.
The current culture is "en-US" - English (United States).
Search for the string "Å" in the string "A Cheshire ca°t"
Part 1: Start index and count are specified.
Comparison: CurrentCulture Location: -1
Comparison: CurrentCultureIgnoreCase Location: 12
Comparison: InvariantCulture Location: -1
Comparison: InvariantCultureIgnoreCase Location: 12
Comparison: Ordinal Location: -1
Comparison: OrdinalIgnoreCase Location: -1
Part 2: Start index is specified.
Comparison: CurrentCulture Location: -1
Comparison: CurrentCultureIgnoreCase Location: 12
Comparison: InvariantCulture Location: -1
Comparison: InvariantCultureIgnoreCase Location: 12
Comparison: Ordinal Location: -1
Comparison: OrdinalIgnoreCase Location: -1
Part 3: Neither start index nor count is specified.
Comparison: CurrentCulture Location: -1
Comparison: CurrentCultureIgnoreCase Location: 12
Comparison: InvariantCulture Location: -1
Comparison: InvariantCultureIgnoreCase Location: 12
Comparison: Ordinal Location: -1
Comparison: OrdinalIgnoreCase Location: -1
*/Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
