Array.LastIndexOf<T> Method (array<T[], T, Int32, Int32)
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Searches for the specified object and returns the index of the last occurrence within the range of elements in the Array that contains the specified number of elements and ends at the specified index.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Shared Function LastIndexOf(Of T) ( _
array As T(), _
value As T, _
startIndex As Integer, _
count As Integer _
) As Integer
public static int LastIndexOf<T>(
T[] array,
T value,
int startIndex,
int count
)
Type Parameters
- T
The type of the elements of the array.
Parameters
- array
Type: array<T[]
The one-dimensional, zero-based Array to search.
- value
Type: T
The object to locate in array.
- 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 range of elements in array that contains the number of elements specified in count and ends at startIndex, if found; otherwise, –1.
Exceptions
| Exception | Condition |
|---|---|
| ArgumentNullException | array is nulla null reference (Nothing in Visual Basic). |
| ArgumentOutOfRangeException | startIndex is outside the range of valid indexes for array. -or- count is less than zero. -or- startIndex and count do not specify a valid section in array. |
Remarks
The Array is searched backward starting at startIndex and ending at startIndex minus count plus 1, if count is greater than 0.
The elements are compared to the specified value using the Object.Equals method. If the element type is a nonintrinsic (user-defined) type, the Equals implementation of that type is used.
This method is an O(n) operation, where n is count.
Examples
The following code example demonstrates all three generic overloads of the LastIndexOf method. An array of strings is created, with one entry that appears twice, at index location 0 and index location 5. The LastIndexOf<T>(array<T[], T) method overload searches the entire array from the end, and finds the second occurrence of the string. The LastIndexOf<T>(array<T[], T, Int32) method overload is used to search the array backward beginning with index location 3 and continuing to the beginning of the array, and finds the first occurrence of the string. Finally, the LastIndexOf<T>(array<T[], T, Int32, Int32) method overload is used to search a range of four entries, beginning at index location 4 and extending backward (that is, it searches the items at locations 4, 3, 2, and 1); this search returns –1 because there are no instances of the search string in that range.
Public Class Example
Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
Dim dinosaurs() As String = {"Tyrannosaurus", _
"Amargasaurus", _
"Mamenchisaurus", _
"Brachiosaurus", _
"Deinonychus", _
"Tyrannosaurus", _
"Compsognathus"}
outputBlock.Text &= vbCrLf
For Each dinosaur As String In dinosaurs
outputBlock.Text &= dinosaur & vbCrLf
Next
outputBlock.Text &= String.Format(vbLf & _
"Array.LastIndexOf(dinosaurs, ""Tyrannosaurus""): {0}", _
Array.LastIndexOf(dinosaurs, "Tyrannosaurus")) & vbCrLf
outputBlock.Text &= String.Format(vbLf & _
"Array.LastIndexOf(dinosaurs, ""Tyrannosaurus"", 3): {0}", _
Array.LastIndexOf(dinosaurs, "Tyrannosaurus", 3)) & vbCrLf
outputBlock.Text &= String.Format(vbLf & _
"Array.LastIndexOf(dinosaurs, ""Tyrannosaurus"", 4, 4): {0}", _
Array.LastIndexOf(dinosaurs, "Tyrannosaurus", 4, 4)) & vbCrLf
End Sub
End Class
' This code example produces the following output:
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Brachiosaurus
'Deinonychus
'Tyrannosaurus
'Compsognathus
'
'Array.LastIndexOf(dinosaurs, "Tyrannosaurus"): 5
'
'Array.LastIndexOf(dinosaurs, "Tyrannosaurus", 3): 0
'
'Array.LastIndexOf(dinosaurs, "Tyrannosaurus", 4, 4): -1
using System;
public class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
string[] dinosaurs = { "Tyrannosaurus",
"Amargasaurus",
"Mamenchisaurus",
"Brachiosaurus",
"Deinonychus",
"Tyrannosaurus",
"Compsognathus" };
outputBlock.Text += "\n";
foreach (string dinosaur in dinosaurs)
{
outputBlock.Text += dinosaur + "\n";
}
outputBlock.Text += String.Format(
"\nArray.LastIndexOf(dinosaurs, \"Tyrannosaurus\"): {0}",
Array.LastIndexOf(dinosaurs, "Tyrannosaurus")) + "\n";
outputBlock.Text += String.Format(
"\nArray.LastIndexOf(dinosaurs, \"Tyrannosaurus\", 3): {0}",
Array.LastIndexOf(dinosaurs, "Tyrannosaurus", 3)) + "\n";
outputBlock.Text += String.Format(
"\nArray.LastIndexOf(dinosaurs, \"Tyrannosaurus\", 4, 4): {0}",
Array.LastIndexOf(dinosaurs, "Tyrannosaurus", 4, 4)) + "\n";
}
}
/* This code example produces the following output:
Tyrannosaurus
Amargasaurus
Mamenchisaurus
Brachiosaurus
Deinonychus
Tyrannosaurus
Compsognathus
Array.LastIndexOf(dinosaurs, "Tyrannosaurus"): 5
Array.LastIndexOf(dinosaurs, "Tyrannosaurus", 3): 0
Array.LastIndexOf(dinosaurs, "Tyrannosaurus", 4, 4): -1
*/
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.