List<T>.FindLastIndex List<T>.FindLastIndex List<T>.FindLastIndex List<T>.FindLastIndex Method

Definição

Pesquisa um elemento que corresponda às condições definidas por um predicado especificado e retorna o índice baseado em zero da última ocorrência no List<T> ou parte dele.Searches for an element that matches the conditions defined by a specified predicate, and returns the zero-based index of the last occurrence within the List<T> or a portion of it.

Sobrecargas

FindLastIndex(Predicate<T>) FindLastIndex(Predicate<T>) FindLastIndex(Predicate<T>) FindLastIndex(Predicate<T>)

Pesquisa um elemento que corresponde às condições definidas pelo predicado especificado e retorna o índice baseado em zero da última ocorrência em toda a List<T>.Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the entire List<T>.

FindLastIndex(Int32, Predicate<T>) FindLastIndex(Int32, Predicate<T>) FindLastIndex(Int32, Predicate<T>) FindLastIndex(Int32, Predicate<T>)

Pesquisa um elemento que corresponde às condições definidas pelo predicado especificado e retorna o índice baseado em zero da última ocorrência dentro do intervalo de elementos no List<T> que se estende do primeiro elemento ao índice especificado.Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the range of elements in the List<T> that extends from the first element to the specified index.

FindLastIndex(Int32, Int32, Predicate<T>) FindLastIndex(Int32, Int32, Predicate<T>) FindLastIndex(Int32, Int32, Predicate<T>) FindLastIndex(Int32, Int32, Predicate<T>)

Pesquisa por um elemento que corresponda às condições definidas pelo predicado especificado e retorna o índice baseado em zero da última ocorrência no intervalo de elementos no List<T> que contém o número de elementos especificado e termina no índice especificado.Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the range of elements in the List<T> that contains the specified number of elements and ends at the specified index.

FindLastIndex(Predicate<T>) FindLastIndex(Predicate<T>) FindLastIndex(Predicate<T>) FindLastIndex(Predicate<T>)

Pesquisa um elemento que corresponde às condições definidas pelo predicado especificado e retorna o índice baseado em zero da última ocorrência em toda a List<T>.Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the entire List<T>.

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

Parâmetros

match
Predicate<T> Predicate<T> Predicate<T> Predicate<T>

O delegado Predicate<T> que define as condições do elemento a ser pesquisado.The Predicate<T> delegate that defines the conditions of the element to search for.

Retornos

O índice de base zero da última ocorrência de um elemento que corresponde às condições definidas por match, se for encontrado; caso contrário, -1.The zero-based index of the last occurrence of an element that matches the conditions defined by match, if found; otherwise, -1.

Exceções

Exemplos

O exemplo a seguir demonstra os métodos de localização para o List<T> classe.The following example demonstrates the find methods for the List<T> class. O exemplo para o List<T> classe contém book objetos da classe Book, usando os dados do arquivo XML de exemplo: Livros (LINQ to XML).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). O FillList usa o método no exemplo LINQ to XML para analisar os valores do XML para valores de propriedade do book objetos.The FillList method in the example uses LINQ to XML to parse the values from the XML to property values of the book objects.

A tabela a seguir descreve os exemplos fornecidos para os métodos find.The following table describes the examples provided for the find methods.

MétodoMethod ExemploExample
Find(Predicate<T>) Localiza um catálogo usando uma ID de IDToFind delegado de predicado.Finds a book by an ID using the IDToFind predicate delegate.

Exemplo de c# usa um delegado anônimo.C# example uses an anonymous delegate.
FindAll(Predicate<T>) Localizar todos os livros que cuja Genre propriedade é "Computador" usando o FindComputer delegado de predicado.Find all books that whose Genre property is "Computer" using the FindComputer predicate delegate.
FindLast(Predicate<T>) Localiza o último registro na coleção que tem uma data de publicação antes de 2001, usando o PubBefore2001 delegado de predicado.Finds the last book in the collection that has a publish date before 2001, using the PubBefore2001 predicate delegate.

Exemplo de c# usa um delegado anônimo.C# example uses an anonymous delegate.
FindIndex(Predicate<T>) Localiza o índice do primeiro livro de computador usando o FindComputer delegado de predicado.Finds the index of first computer book using the FindComputer predicate delegate.
FindLastIndex(Predicate<T>) Localiza o índice do último livro computador usando o FindComputer delegado de predicado.Finds the index of the last computer book using the FindComputer predicate delegate.
FindIndex(Int32, Int32, Predicate<T>) Localiza o índice do primeiro livro de computador na segunda metade da coleção, usando o FindComputer delegado de predicado.Finds the index of first computer book in the second half of the collection, using the FindComputer predicate delegate.
FindLastIndex(Int32, Int32, Predicate<T>) Localiza o índice do último registro de computador na segunda metade da coleção, usando o FindComputer delegado de predicado.Finds the index of last computer book in the second half of the collection, using the FindComputer predicate delegate.
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

Comentários

O List<T> é pesquisado para trás começando no último elemento e terminando no primeiro elemento.The List<T> is searched backward starting at the last element and ending at the first element.

O Predicate<T> é um representante para um método que retorna true caso o objeto passado para ele corresponda às condições definidas no representante.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. Os elementos do atual List<T> são passados individualmente para o Predicate<T> delegar.The elements of the current List<T> are individually passed to the Predicate<T> delegate.

Esse método executa uma pesquisa linear. Portanto, esse método é um O (n) a operação, onde n é Count.This method performs a linear search; therefore, this method is an O(n) operation, where n is Count.

Veja também

FindLastIndex(Int32, Predicate<T>) FindLastIndex(Int32, Predicate<T>) FindLastIndex(Int32, Predicate<T>) FindLastIndex(Int32, Predicate<T>)

Pesquisa um elemento que corresponde às condições definidas pelo predicado especificado e retorna o índice baseado em zero da última ocorrência dentro do intervalo de elementos no List<T> que se estende do primeiro elemento ao índice especificado.Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the range of elements in the List<T> that extends from the first element to the specified index.

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

Parâmetros

startIndex
Int32 Int32 Int32 Int32

O índice inicial com base em zero da pesquisa inversa.The zero-based starting index of the backward search.

match
Predicate<T> Predicate<T> Predicate<T> Predicate<T>

O delegado Predicate<T> que define as condições do elemento a ser pesquisado.The Predicate<T> delegate that defines the conditions of the element to search for.

Retornos

O índice de base zero da última ocorrência de um elemento que corresponde às condições definidas por match, se for encontrado; caso contrário, -1.The zero-based index of the last occurrence of an element that matches the conditions defined by match, if found; otherwise, -1.

Exceções

startIndex está fora do intervalo de índices válidos para o List<T>.startIndex is outside the range of valid indexes for the List<T>.

Comentários

O List<T> é pesquisada começando com versões anteriores em startIndex e terminando no primeiro elemento.The List<T> is searched backward starting at startIndex and ending at the first element.

O Predicate<T> é um representante para um método que retorna true caso o objeto passado para ele corresponda às condições definidas no representante.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. Os elementos do atual List<T> são passados individualmente para o Predicate<T> delegar.The elements of the current List<T> are individually passed to the Predicate<T> delegate.

Esse método executa uma pesquisa linear. Portanto, esse método é um O (n) a operação, onde n é o número de elementos desde o início do List<T> para startIndex.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.

Veja também

FindLastIndex(Int32, Int32, Predicate<T>) FindLastIndex(Int32, Int32, Predicate<T>) FindLastIndex(Int32, Int32, Predicate<T>) FindLastIndex(Int32, Int32, Predicate<T>)

Pesquisa por um elemento que corresponda às condições definidas pelo predicado especificado e retorna o índice baseado em zero da última ocorrência no intervalo de elementos no List<T> que contém o número de elementos especificado e termina no índice especificado.Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the range of elements in the List<T> that contains the specified number of elements and ends at the specified index.

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

Parâmetros

startIndex
Int32 Int32 Int32 Int32

O índice inicial com base em zero da pesquisa inversa.The zero-based starting index of the backward search.

count
Int32 Int32 Int32 Int32

O número de elementos na seção a ser pesquisada.The number of elements in the section to search.

match
Predicate<T> Predicate<T> Predicate<T> Predicate<T>

O delegado Predicate<T> que define as condições do elemento a ser pesquisado.The Predicate<T> delegate that defines the conditions of the element to search for.

Retornos

O índice de base zero da última ocorrência de um elemento que corresponde às condições definidas por match, se for encontrado; caso contrário, -1.The zero-based index of the last occurrence of an element that matches the conditions defined by match, if found; otherwise, -1.

Exceções

startIndex está fora do intervalo de índices válidos para o List<T>.startIndex is outside the range of valid indexes for the List<T>.

- ou --or- count é menor que 0.count is less than 0.

- ou --or- startIndex e count não especificam uma seção válida no List<T>.startIndex and count do not specify a valid section in the List<T>.

Exemplos

O exemplo a seguir demonstra os métodos de localização para o List<T> classe.The following example demonstrates the find methods for the List<T> class. O exemplo para o List<T> classe contém book objetos da classe Book, usando os dados do arquivo XML de exemplo: Livros (LINQ to XML).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). O FillList usa o método no exemplo LINQ to XML para analisar os valores do XML para valores de propriedade do book objetos.The FillList method in the example uses LINQ to XML to parse the values from the XML to property values of the book objects.

A tabela a seguir descreve os exemplos fornecidos para os métodos find.The following table describes the examples provided for the find methods.

MétodoMethod ExemploExample
Find(Predicate<T>) Localiza um catálogo usando uma ID de IDToFind delegado de predicado.Finds a book by an ID using the IDToFind predicate delegate.

Exemplo de c# usa um delegado anônimo.C# example uses an anonymous delegate.
FindAll(Predicate<T>) Localizar todos os livros que cuja Genre propriedade é "Computador" usando o FindComputer delegado de predicado.Find all books that whose Genre property is "Computer" using the FindComputer predicate delegate.
FindLast(Predicate<T>) Localiza o último registro na coleção que tem uma data de publicação antes de 2001, usando o PubBefore2001 delegado de predicado.Finds the last book in the collection that has a publish date before 2001, using the PubBefore2001 predicate delegate.

Exemplo de c# usa um delegado anônimo.C# example uses an anonymous delegate.
FindIndex(Predicate<T>) Localiza o índice do primeiro livro de computador usando o FindComputer delegado de predicado.Finds the index of first computer book using the FindComputer predicate delegate.
FindLastIndex(Predicate<T>) Localiza o índice do último livro computador usando o FindComputer delegado de predicado.Finds the index of the last computer book using the FindComputer predicate delegate.
FindIndex(Int32, Int32, Predicate<T>) Localiza o índice do primeiro livro de computador na segunda metade da coleção, usando o FindComputer delegado de predicado.Finds the index of first computer book in the second half of the collection, using the FindComputer predicate delegate.
FindLastIndex(Int32, Int32, Predicate<T>) Localiza o índice do último registro de computador na segunda metade da coleção, usando o FindComputer delegado de predicado.Finds the index of last computer book in the second half of the collection, using the FindComputer predicate delegate.
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

Comentários

O List<T> é pesquisada com versões anteriores começando startIndex e termina em startIndex menos count mais 1, se count for maior que 0.The List<T> is searched backward starting at startIndex and ending at startIndex minus count plus 1, if count is greater than 0.

O Predicate<T> é um representante para um método que retorna true caso o objeto passado para ele corresponda às condições definidas no representante.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. Os elementos do atual List<T> são passados individualmente para o Predicate<T> delegar.The elements of the current List<T> are individually passed to the Predicate<T> delegate.

Esse método executa uma pesquisa linear. Portanto, esse método é um O (n) a operação, onde n é count.This method performs a linear search; therefore, this method is an O(n) operation, where n is count.

Veja também

Aplica-se a