List<T>.FindLastIndex Method

Source:

List.cs

Source:

List.cs

Source:

List.cs

Source:

List.cs

Source:

List.cs

public:
 int FindLastIndex(Predicate<T> ^ match);

public int FindLastIndex(Predicate<T> match);

member this.FindLastIndex : Predicate<'T> -> int

Public Function FindLastIndex (match As Predicate(Of T)) As Integer

Parameters

Returns

The zero-based index of the last occurrence of an element that matches the conditions defined by match, if found; otherwise, -1.

Exceptions

Examples

The following example demonstrates the find methods for the List<T> class. The example for the List<T> class contains book objects, of class Book, using the data from the Sample XML File: Books (LINQ to XML). The FillList method in the example uses LINQ to XML to parse the values from the XML to property values of the book objects.

The following table describes the examples provided for the find methods.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;

namespace Find
{
 class Program
 {
 private static string IDtoFind = "bk109";

 private static List<Book> Books = new List<Book>();
 public static void Main(string[] args)
 {
 FillList();

 // Find a book by its ID.
 Book result = Books.Find(
 delegate(Book bk)
 {
 return bk.ID == IDtoFind;
 }
 );
 if (result != null)
 {
 DisplayResult(result, "Find by ID: " + IDtoFind);
 }
 else
 {
 Console.WriteLine("\nNot found: {0}", IDtoFind);
 }

 // Find last book in collection published before 2001.
 result = Books.FindLast(
 delegate(Book bk)
 {
 DateTime year2001 = new DateTime(2001,01,01);
 return bk.Publish_date < year2001;
 });
 if (result != null)
 {
 DisplayResult(result, "Last book in collection published before 2001:");
 }
 else
 {
 Console.WriteLine("\nNot found: {0}", IDtoFind);
 }

 // Find all computer books.
 List<Book> results = Books.FindAll(FindComputer);
 if (results.Count != 0)
 {
 DisplayResults(results, "All computer:");
 }
 else
 {
 Console.WriteLine("\nNo books found.");
 }

 // Find all books under $10.00.
 results = Books.FindAll(
 delegate(Book bk)
 {
 return bk.Price < 10.00;
 }
 );
 if (results.Count != 0)
 {
 DisplayResults(results, "Books under $10:");
 }
 else
 {
 Console.WriteLine("\nNo books found.");
 }

 // Find index values.
 Console.WriteLine();
 int ndx = Books.FindIndex(FindComputer);
 Console.WriteLine("Index of first computer book: {0}", ndx);
 ndx = Books.FindLastIndex(FindComputer);
 Console.WriteLine("Index of last computer book: {0}", ndx);

 int mid = Books.Count / 2;
 ndx = Books.FindIndex(mid, mid, FindComputer);
 Console.WriteLine("Index of first computer book in the second half of the collection: {0}", ndx);

 ndx = Books.FindLastIndex(Books.Count - 1, mid, FindComputer);
 Console.WriteLine("Index of last computer book in the second half of the collection: {0}", ndx);
 }

 // Populates the list with sample data.
 private static void FillList()
 {

 // Create XML elements from a source file.
 XElement xTree = XElement.Load(@"c:\temp\books.xml");

 // Create an enumerable collection of the elements.
 IEnumerable<XElement> elements = xTree.Elements();

 // Evaluate each element and set set values in the book object.
 foreach (XElement el in elements)
 {
 Book book = new Book();
 book.ID = el.Attribute("id").Value;
 IEnumerable<XElement> props = el.Elements();
 foreach (XElement p in props)
 {

 if (p.Name.ToString().ToLower() == "author")
 {
 book.Author = p.Value;
 }
 else if (p.Name.ToString().ToLower() == "title")
 {
 book.Title = p.Value;
 }
 else if (p.Name.ToString().ToLower() == "genre")
 {
 book.Genre = p.Value;
 }
 else if (p.Name.ToString().ToLower() == "price")
 {
 book.Price = Convert.ToDouble(p.Value);
 }
 else if (p.Name.ToString().ToLower() == "publish_date")
 {
 book.Publish_date = Convert.ToDateTime(p.Value);
 }
 else if (p.Name.ToString().ToLower() == "description")
 {
 book.Description = p.Value;
 }
 }

 Books.Add(book);
 }

 DisplayResults(Books, "All books:");
 }

 // Explicit predicate delegate.
 private static bool FindComputer(Book bk)
 {

 if (bk.Genre == "Computer")
 {
 return true;
 }
 else
 {
 return false;
 }
 }

 private static void DisplayResult(Book result, string title)
 {
 Console.WriteLine();
 Console.WriteLine(title);
 Console.WriteLine("\n{0}\t{1}\t{2}\t{3}\t{4}\t{5}", result.ID,
 result.Author, result.Title, result.Genre, result.Price,
 result.Publish_date.ToShortDateString());
 Console.WriteLine();
 }

 private static void DisplayResults(List<Book> results, string title)
 {
 Console.WriteLine();
 Console.WriteLine(title);
 foreach (Book b in results)
 {

 Console.Write("\n{0}\t{1}\t{2}\t{3}\t{4}\t{5}", b.ID,
 b.Author, b.Title, b.Genre, b.Price,
 b.Publish_date.ToShortDateString());
 }
 Console.WriteLine();
 }
 }

 public class Book
 {
 public string ID { get; set; }
 public string Author { get; set; }
 public string Title { get; set; }
 public string Genre { get; set; }
 public double Price { get; set; }
 public DateTime Publish_date { get; set; }
 public string Description { get; set; }
 }
}

Imports System.Collections.Generic
Imports System.Linq
Imports System.Xml.Linq
Module Module1

 Private IDToFind As String = "bk109"

 Public Books As New List(Of Book)


 Sub Main()

 FillList()

 ' Find a book by its ID.
 Dim result As Book = Books.Find(AddressOf FindID)
 If result IsNot Nothing Then
 DisplayResult(result, "Find by ID: " & IDToFind)
 Else

 Console.WriteLine(vbCrLf & "Not found: " & IDToFind)
 End If
 Console.WriteLine()

 ' Find last book in collection that has a publish date before 2001.
 result = Books.FindLast(AddressOf PubBefore2001)
 If result IsNot Nothing Then
 DisplayResult(result, "Last book in collection published before 2001:")
 Else
 Console.WriteLine(vbCrLf & "Not found: " & IDToFind)
 End If
 Console.WriteLine()

 ' Find all computer books.
 Dim results As List(Of Book) = Books.FindAll(AddressOf FindComputer)
 If results.Count <> 0 Then
 DisplayResults(results, "All computer books:")
 Else
 Console.WriteLine(vbCrLf & "No books found.")
 End If
 Console.WriteLine()


 ' Find all books under $10.00.
 results = Books.FindAll(AddressOf FindUnderTen)
 If results.Count <> 0 Then
 DisplayResults(results, "Books under $10:")
 Else
 Console.WriteLine(vbCrLf & "No books found.")
 End If
 Console.WriteLine()

 ' Find index values.
 Console.WriteLine()
 Dim ndx As Integer = Books.FindIndex(AddressOf FindComputer)
 Console.WriteLine("Index of first computer book: " & ndx)
 ndx = Books.FindLastIndex(AddressOf FindComputer)
 Console.WriteLine("Index of last computer book: " & ndx)

 Dim mid As Integer = Books.Count / 2
 ndx = Books.FindIndex(mid, mid, AddressOf FindComputer)
 Console.WriteLine("Index of first computer book in the second half of the collection: " & ndx)



 ndx = Books.FindLastIndex(Books.Count - 1, mid, AddressOf FindComputer)
 Console.WriteLine("Index of last computer book in the second half of the collection: " & ndx)


 End Sub



 Private Sub FillList()

 ' Create XML elements from a source file.
 Dim xTree As XElement = XElement.Load("c:\temp\books.xml")

 ' Create an enumerable collection of the elements.
 Dim elements As IEnumerable(Of XElement) = xTree.Elements

 ' Evaluate each element and set values in the book object.
 For Each el As XElement In elements
 Dim Book As New Book()
 Book.ID = el.Attribute("id").Value
 Dim props As IEnumerable(Of XElement) = el.Elements
 For Each p As XElement In props
 If p.Name.ToString.ToLower = "author" Then
 Book.Author = p.Value
 End If
 If p.Name.ToString.ToLower = "title" Then
 Book.Title = p.Value
 End If
 If p.Name.ToString.ToLower = "genre" Then
 Book.Genre = p.Value
 End If
 If p.Name.ToString.ToLower = "price" Then
 Book.Price = Convert.ToDouble(p.Value)
 End If
 If p.Name.ToString.ToLower = "publish_date" Then
 Book.Publish_date = Convert.ToDateTime(p.Value)
 End If
 If p.Name.ToString.ToLower = "description" Then
 Book.Description = p.Value
 End If
 Next
 Books.Add(Book)
 Next

 DisplayResults(Books, "All books:")
 Console.WriteLine()

 End Sub

 ' Predicate delegates for
 ' Find and FindAll methods.
 Private Function FindID(ByVal bk As Book) As Boolean
 If bk.ID = IDToFind Then
 Return True
 Else
 Return False
 End If
 End Function
 Private Function FindComputer(ByVal bk As Book) As Boolean
 If bk.Genre = "Computer" Then
 Return True
 Else
 Return False
 End If
 End Function
 Private Function FindUnderTen(ByVal bk As Book) As Boolean
 Dim tendollars As Double = 10.0
 If bk.Price < tendollars Then
 Return True
 Else
 Return False
 End If
 End Function
 Private Function PubBefore2001(ByVal bk As Book) As Boolean
 Dim year2001 As DateTime = New DateTime(2001, 1, 1)
 Return bk.Publish_date < year2001
 End Function
 Private Sub DisplayResult(ByVal result As Book, ByVal title As String)
 Console.WriteLine()
 Console.WriteLine(title)
 Console.WriteLine(vbLf & result.ID & vbTab & result.Author & _
 vbTab & result.Title & vbTab & result.Genre & _
 vbTab & result.Publish_date & vbTab & result.Price)
 Console.WriteLine()
 End Sub
 Private Sub DisplayResults(ByVal results As List(Of Book), ByVal title As String)
 Console.WriteLine()
 Console.WriteLine(title)
 For Each b As Book In results
 Console.Write(vbLf & b.ID & vbTab & b.Author & _
 vbTab & b.Title & vbTab & b.Genre & _
 vbTab & b.Publish_date & vbTab & b.Price)
 Next
 Console.WriteLine()
 End Sub

 Public Class Book
 Public ID As String
 Public Author As String
 Public Title As String
 Public Genre As String
 Public Price As Double
 Public Publish_date As DateTime
 Public Description As String
 End Class


End Module

Remarks

The List<T> is searched backward starting at the last element and ending at the first element.

The Predicate<T> is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. The elements of the current List<T> are individually passed to the Predicate<T> delegate.

This method performs a linear search; therefore, this method is an O(n) operation, where n is Count.

See also

• Exists(Predicate<T>)
• Find(Predicate<T>)
• FindLast(Predicate<T>)
• FindAll(Predicate<T>)
• FindIndex
• BinarySearch
• IndexOf
• LastIndexOf
• Predicate<T>

Source:

List.cs

Source:

List.cs

Source:

List.cs

Source:

List.cs

Source:

List.cs

public:
 int FindLastIndex(int startIndex, Predicate<T> ^ match);

public int FindLastIndex(int startIndex, Predicate<T> match);

member this.FindLastIndex : int * Predicate<'T> -> int

Public Function FindLastIndex (startIndex As Integer, match As Predicate(Of T)) As Integer

Parameters

Returns

The zero-based index of the last occurrence of an element that matches the conditions defined by match, if found; otherwise, -1.

Exceptions

Remarks

The List<T> is searched backward starting at startIndex and ending at the first element.

The Predicate<T> is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. The elements of the current List<T> are individually passed to the Predicate<T> delegate.

This method performs a linear search; therefore, this method is an O(n) operation, where n is the number of elements from the beginning of the List<T> to startIndex.

See also

• Exists(Predicate<T>)
• Find(Predicate<T>)
• FindLast(Predicate<T>)
• FindAll(Predicate<T>)
• FindIndex
• BinarySearch
• IndexOf
• LastIndexOf
• Predicate<T>

Source:

List.cs

Source:

List.cs

Source:

List.cs

Source:

List.cs

Source:

List.cs

public:
 int FindLastIndex(int startIndex, int count, Predicate<T> ^ match);

public int FindLastIndex(int startIndex, int count, Predicate<T> match);

member this.FindLastIndex : int * int * Predicate<'T> -> int

Public Function FindLastIndex (startIndex As Integer, count As Integer, match As Predicate(Of T)) As Integer

Parameters

Returns

The zero-based index of the last occurrence of an element that matches the conditions defined by match, if found; otherwise, -1.

Exceptions

Examples

The following example demonstrates the find methods for the List<T> class. The example for the List<T> class contains book objects, of class Book, using the data from the Sample XML File: Books (LINQ to XML). The FillList method in the example uses LINQ to XML to parse the values from the XML to property values of the book objects.

The following table describes the examples provided for the find methods.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;

namespace Find
{
 class Program
 {
 private static string IDtoFind = "bk109";

 private static List<Book> Books = new List<Book>();
 public static void Main(string[] args)
 {
 FillList();

 // Find a book by its ID.
 Book result = Books.Find(
 delegate(Book bk)
 {
 return bk.ID == IDtoFind;
 }
 );
 if (result != null)
 {
 DisplayResult(result, "Find by ID: " + IDtoFind);
 }
 else
 {
 Console.WriteLine("\nNot found: {0}", IDtoFind);
 }

 // Find last book in collection published before 2001.
 result = Books.FindLast(
 delegate(Book bk)
 {
 DateTime year2001 = new DateTime(2001,01,01);
 return bk.Publish_date < year2001;
 });
 if (result != null)
 {
 DisplayResult(result, "Last book in collection published before 2001:");
 }
 else
 {
 Console.WriteLine("\nNot found: {0}", IDtoFind);
 }

 // Find all computer books.
 List<Book> results = Books.FindAll(FindComputer);
 if (results.Count != 0)
 {
 DisplayResults(results, "All computer:");
 }
 else
 {
 Console.WriteLine("\nNo books found.");
 }

 // Find all books under $10.00.
 results = Books.FindAll(
 delegate(Book bk)
 {
 return bk.Price < 10.00;
 }
 );
 if (results.Count != 0)
 {
 DisplayResults(results, "Books under $10:");
 }
 else
 {
 Console.WriteLine("\nNo books found.");
 }

 // Find index values.
 Console.WriteLine();
 int ndx = Books.FindIndex(FindComputer);
 Console.WriteLine("Index of first computer book: {0}", ndx);
 ndx = Books.FindLastIndex(FindComputer);
 Console.WriteLine("Index of last computer book: {0}", ndx);

 int mid = Books.Count / 2;
 ndx = Books.FindIndex(mid, mid, FindComputer);
 Console.WriteLine("Index of first computer book in the second half of the collection: {0}", ndx);

 ndx = Books.FindLastIndex(Books.Count - 1, mid, FindComputer);
 Console.WriteLine("Index of last computer book in the second half of the collection: {0}", ndx);
 }

 // Populates the list with sample data.
 private static void FillList()
 {

 // Create XML elements from a source file.
 XElement xTree = XElement.Load(@"c:\temp\books.xml");

 // Create an enumerable collection of the elements.
 IEnumerable<XElement> elements = xTree.Elements();

 // Evaluate each element and set set values in the book object.
 foreach (XElement el in elements)
 {
 Book book = new Book();
 book.ID = el.Attribute("id").Value;
 IEnumerable<XElement> props = el.Elements();
 foreach (XElement p in props)
 {

 if (p.Name.ToString().ToLower() == "author")
 {
 book.Author = p.Value;
 }
 else if (p.Name.ToString().ToLower() == "title")
 {
 book.Title = p.Value;
 }
 else if (p.Name.ToString().ToLower() == "genre")
 {
 book.Genre = p.Value;
 }
 else if (p.Name.ToString().ToLower() == "price")
 {
 book.Price = Convert.ToDouble(p.Value);
 }
 else if (p.Name.ToString().ToLower() == "publish_date")
 {
 book.Publish_date = Convert.ToDateTime(p.Value);
 }
 else if (p.Name.ToString().ToLower() == "description")
 {
 book.Description = p.Value;
 }
 }

 Books.Add(book);
 }

 DisplayResults(Books, "All books:");
 }

 // Explicit predicate delegate.
 private static bool FindComputer(Book bk)
 {

 if (bk.Genre == "Computer")
 {
 return true;
 }
 else
 {
 return false;
 }
 }

 private static void DisplayResult(Book result, string title)
 {
 Console.WriteLine();
 Console.WriteLine(title);
 Console.WriteLine("\n{0}\t{1}\t{2}\t{3}\t{4}\t{5}", result.ID,
 result.Author, result.Title, result.Genre, result.Price,
 result.Publish_date.ToShortDateString());
 Console.WriteLine();
 }

 private static void DisplayResults(List<Book> results, string title)
 {
 Console.WriteLine();
 Console.WriteLine(title);
 foreach (Book b in results)
 {

 Console.Write("\n{0}\t{1}\t{2}\t{3}\t{4}\t{5}", b.ID,
 b.Author, b.Title, b.Genre, b.Price,
 b.Publish_date.ToShortDateString());
 }
 Console.WriteLine();
 }
 }

 public class Book
 {
 public string ID { get; set; }
 public string Author { get; set; }
 public string Title { get; set; }
 public string Genre { get; set; }
 public double Price { get; set; }
 public DateTime Publish_date { get; set; }
 public string Description { get; set; }
 }
}

Imports System.Collections.Generic
Imports System.Linq
Imports System.Xml.Linq
Module Module1

 Private IDToFind As String = "bk109"

 Public Books As New List(Of Book)


 Sub Main()

 FillList()

 ' Find a book by its ID.
 Dim result As Book = Books.Find(AddressOf FindID)
 If result IsNot Nothing Then
 DisplayResult(result, "Find by ID: " & IDToFind)
 Else

 Console.WriteLine(vbCrLf & "Not found: " & IDToFind)
 End If
 Console.WriteLine()

 ' Find last book in collection that has a publish date before 2001.
 result = Books.FindLast(AddressOf PubBefore2001)
 If result IsNot Nothing Then
 DisplayResult(result, "Last book in collection published before 2001:")
 Else
 Console.WriteLine(vbCrLf & "Not found: " & IDToFind)
 End If
 Console.WriteLine()

 ' Find all computer books.
 Dim results As List(Of Book) = Books.FindAll(AddressOf FindComputer)
 If results.Count <> 0 Then
 DisplayResults(results, "All computer books:")
 Else
 Console.WriteLine(vbCrLf & "No books found.")
 End If
 Console.WriteLine()


 ' Find all books under $10.00.
 results = Books.FindAll(AddressOf FindUnderTen)
 If results.Count <> 0 Then
 DisplayResults(results, "Books under $10:")
 Else
 Console.WriteLine(vbCrLf & "No books found.")
 End If
 Console.WriteLine()

 ' Find index values.
 Console.WriteLine()
 Dim ndx As Integer = Books.FindIndex(AddressOf FindComputer)
 Console.WriteLine("Index of first computer book: " & ndx)
 ndx = Books.FindLastIndex(AddressOf FindComputer)
 Console.WriteLine("Index of last computer book: " & ndx)

 Dim mid As Integer = Books.Count / 2
 ndx = Books.FindIndex(mid, mid, AddressOf FindComputer)
 Console.WriteLine("Index of first computer book in the second half of the collection: " & ndx)



 ndx = Books.FindLastIndex(Books.Count - 1, mid, AddressOf FindComputer)
 Console.WriteLine("Index of last computer book in the second half of the collection: " & ndx)


 End Sub



 Private Sub FillList()

 ' Create XML elements from a source file.
 Dim xTree As XElement = XElement.Load("c:\temp\books.xml")

 ' Create an enumerable collection of the elements.
 Dim elements As IEnumerable(Of XElement) = xTree.Elements

 ' Evaluate each element and set values in the book object.
 For Each el As XElement In elements
 Dim Book As New Book()
 Book.ID = el.Attribute("id").Value
 Dim props As IEnumerable(Of XElement) = el.Elements
 For Each p As XElement In props
 If p.Name.ToString.ToLower = "author" Then
 Book.Author = p.Value
 End If
 If p.Name.ToString.ToLower = "title" Then
 Book.Title = p.Value
 End If
 If p.Name.ToString.ToLower = "genre" Then
 Book.Genre = p.Value
 End If
 If p.Name.ToString.ToLower = "price" Then
 Book.Price = Convert.ToDouble(p.Value)
 End If
 If p.Name.ToString.ToLower = "publish_date" Then
 Book.Publish_date = Convert.ToDateTime(p.Value)
 End If
 If p.Name.ToString.ToLower = "description" Then
 Book.Description = p.Value
 End If
 Next
 Books.Add(Book)
 Next

 DisplayResults(Books, "All books:")
 Console.WriteLine()

 End Sub

 ' Predicate delegates for
 ' Find and FindAll methods.
 Private Function FindID(ByVal bk As Book) As Boolean
 If bk.ID = IDToFind Then
 Return True
 Else
 Return False
 End If
 End Function
 Private Function FindComputer(ByVal bk As Book) As Boolean
 If bk.Genre = "Computer" Then
 Return True
 Else
 Return False
 End If
 End Function
 Private Function FindUnderTen(ByVal bk As Book) As Boolean
 Dim tendollars As Double = 10.0
 If bk.Price < tendollars Then
 Return True
 Else
 Return False
 End If
 End Function
 Private Function PubBefore2001(ByVal bk As Book) As Boolean
 Dim year2001 As DateTime = New DateTime(2001, 1, 1)
 Return bk.Publish_date < year2001
 End Function
 Private Sub DisplayResult(ByVal result As Book, ByVal title As String)
 Console.WriteLine()
 Console.WriteLine(title)
 Console.WriteLine(vbLf & result.ID & vbTab & result.Author & _
 vbTab & result.Title & vbTab & result.Genre & _
 vbTab & result.Publish_date & vbTab & result.Price)
 Console.WriteLine()
 End Sub
 Private Sub DisplayResults(ByVal results As List(Of Book), ByVal title As String)
 Console.WriteLine()
 Console.WriteLine(title)
 For Each b As Book In results
 Console.Write(vbLf & b.ID & vbTab & b.Author & _
 vbTab & b.Title & vbTab & b.Genre & _
 vbTab & b.Publish_date & vbTab & b.Price)
 Next
 Console.WriteLine()
 End Sub

 Public Class Book
 Public ID As String
 Public Author As String
 Public Title As String
 Public Genre As String
 Public Price As Double
 Public Publish_date As DateTime
 Public Description As String
 End Class


End Module

Remarks

The List<T> is searched backward starting at startIndex and ending at startIndex minus count plus 1, if count is greater than 0.

The Predicate<T> is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. The elements of the current List<T> are individually passed to the Predicate<T> delegate.

This method performs a linear search; therefore, this method is an O(n) operation, where n is count.

See also

• Exists(Predicate<T>)
• Find(Predicate<T>)
• FindLast(Predicate<T>)
• FindAll(Predicate<T>)
• FindIndex
• BinarySearch
• IndexOf
• LastIndexOf
• Predicate<T>