String.LastIndexOf Method (Char, Int32)
Microsoft Silverlight will reach end of support after October 2021. Learn more.
Reports the zero-based index position of the last occurrence of a specified Unicode character within this instance. The search starts at a specified character position.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Function LastIndexOf ( _
value As Char, _
startIndex As Integer _
) As Integer
public int LastIndexOf(
char value,
int startIndex
)
Parameters
- value
Type: System.Char
A Unicode character to seek.
- startIndex
Type: System.Int32
The starting position of a substring within this instance.
Return Value
Type: System.Int32
The zero-based index position of value if that character is found, or -1 if it is not found or if the current instance equals String.Empty.
Exceptions
| Exception | Condition |
|---|---|
| ArgumentOutOfRangeException | The current instance does not equal String.Empty and startIndex is less than zero or greater than or equal to the length of this instance. |
Remarks
Index numbering starts from zero. That is, the first character in the string is at index zero and the last is at Length - 1. This method begins searching at the startIndex character position of this instance and proceeds backward toward the beginning until either value is found or the first character position has been examined. For example, if startIndex is Length - 1, the method searches every character from the last character in the string to the beginning. The search is case-sensitive.
This method performs an ordinal (culture-insensitive) search, where a character is considered equivalent to another character only if their Unicode scalar values are the same. To perform a culture-sensitive search, use the CompareInfo.LastIndexOf method, where a Unicode scalar value representing a precomposed character, such as the ligature 'Æ' (U+00C6), might be considered equivalent to any occurrence of the character's components in the correct sequence, such as "AE" (U+0041, U+0045), depending on the culture.
Examples
The following code example finds the index of all occurrences of a character in a string, working from the end of the string to the start of the string.
' Sample for String.LastIndexOf(Char, Int32)
_
Class Example
Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
Dim br1 As String = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-"
Dim br2 As String = "0123456789012345678901234567890123456789012345678901234567890123456"
Dim str As String = "Now is the time for all good men to come to the aid of their party."
Dim start As Integer
Dim at As Integer
start = str.Length - 1
outputBlock.Text &= String.Format("All occurrences of 't' from position {0} to 0.", start) & vbCrLf
outputBlock.Text &= String.Format("{1}{0}{2}{0}{3}{0}", vbCrLf, br1, br2, str) & vbCrLf
outputBlock.Text &= "The letter 't' occurs at position(s): "
at = 0
While start > -1 And at > -1
at = str.LastIndexOf("t"c, start)
If at > -1 Then
outputBlock.Text &= String.Format("{0} ", at)
start = at - 1
End If
End While
outputBlock.Text &= String.Format("{0}{0}{0}", vbCrLf)
End Sub 'Main
End Class 'Sample
'
'This example produces the following results:
'All occurrences of 't' from position 66 to 0.
'0----+----1----+----2----+----3----+----4----+----5----+----6----+-
'0123456789012345678901234567890123456789012345678901234567890123456
'Now is the time for all good men to come to the aid of their party.
'
'The letter 't' occurs at position(s): 64 55 44 41 33 11 7
'
// Sample for String.LastIndexOf(Char, Int32)
using System;
class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
string br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
string br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
string str = "Now is the time for all good men to come to the aid of their party.";
int start;
int at;
start = str.Length - 1;
outputBlock.Text += String.Format("All occurrences of 't' from position {0} to 0.", start) + "\n";
outputBlock.Text += String.Format("{1}{0}{2}{0}{3}{0}", "\n", br1, br2, str) + "\n";
outputBlock.Text += "The letter 't' occurs at position(s): ";
at = 0;
while ((start > -1) && (at > -1))
{
at = str.LastIndexOf('t', start);
if (at > -1)
{
outputBlock.Text += String.Format("{0} ", at);
start = at - 1;
}
}
outputBlock.Text += String.Format("{0}{0}{0}", "\n");
}
}
/*
This example produces the following results:
All occurrences of 't' from position 66 to 0.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.
The letter 't' occurs at position(s): 64 55 44 41 33 11 7
*/
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