List<T>.FindLast(Predicate<T>) 메서드

정의

지정된 조건자에 정의된 조건과 일치하는 요소를 검색하고 전체 List<T>에서 마지막으로 검색한 요소를 반환합니다.Searches for an element that matches the conditions defined by the specified predicate, and returns the last occurrence within the entire List<T>.

public:
 T FindLast(Predicate<T> ^ match);
public T FindLast (Predicate<T> match);
member this.FindLast : Predicate<'T> -> 'T
Public Function FindLast (match As Predicate(Of T)) As T

매개 변수

match
Predicate<T>

검색할 요소의 조건을 정의하는 Predicate<T> 대리자입니다.The Predicate<T> delegate that defines the conditions of the element to search for.

반환

T

지정된 조건자에 정의된 조건과 일치하는 요소가 있으면 일치하는 요소 중 마지막 요소이고, 그렇지 않으면 T 형식의 기본값입니다.The last element that matches the conditions defined by the specified predicate, if found; otherwise, the default value for type T.

예외

matchnull인 경우match is null.

예제

다음 예제에서는 List<T> 클래스에 대 한 find 메서드를 보여 줍니다.The following example demonstrates the find methods for the List<T> class. List<T> 클래스에 대 한 예제에는 샘플 XML 파일: Books (LINQ to XML)의 데이터를 사용 하 여 클래스 Bookbook 개체가 포함 되어 있습니다.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). 예제의 FillList 메서드는 LINQ to XML 를 사용 하 여 book 개체의 XML에서 속성 값으로의 값을 구문 분석 합니다.The FillList method in the example uses LINQ to XML to parse the values from the XML to property values of the book objects.

다음 표에서 find 메서드에 제공 된 예제를 설명 합니다.The following table describes the examples provided for the find methods.

메서드Method 예제Example
Find(Predicate<T>) IDToFind 조건자 대리자를 사용 하 여 ID로 책을 찾습니다.Finds a book by an ID using the IDToFind predicate delegate.

C# 예제에서는 익명 대리자를 사용합니다.C# example uses an anonymous delegate.
FindAll(Predicate<T>) Genre 속성이 FindComputer 조건자 대리자를 사용 하 여 "Computer" 인 모든 책을 찾습니다.Find all books that whose Genre property is "Computer" using the FindComputer predicate delegate.
FindLast(Predicate<T>) PubBefore2001 조건자 대리자를 사용 하 여 2001 이전의 게시 날짜가 있는 컬렉션에서 마지막 책을 찾습니다.Finds the last book in the collection that has a publish date before 2001, using the PubBefore2001 predicate delegate.

C# 예제에서는 익명 대리자를 사용합니다.C# example uses an anonymous delegate.
FindIndex(Predicate<T>) FindComputer 조건자 대리자를 사용 하 여 첫 번째 컴퓨터의 인덱스를 찾습니다.Finds the index of first computer book using the FindComputer predicate delegate.
FindLastIndex(Predicate<T>) FindComputer 조건자 대리자를 사용 하 여 마지막 컴퓨터 책의 인덱스를 찾습니다.Finds the index of the last computer book using the FindComputer predicate delegate.
FindIndex(Int32, Int32, Predicate<T>) FindComputer 조건자 대리자를 사용 하 여 컬렉션의 두 번째 부분에서 첫 번째 컴퓨터 책의 인덱스를 찾습니다.Finds the index of first computer book in the second half of the collection, using the FindComputer predicate delegate.
FindLastIndex(Int32, Int32, Predicate<T>) FindComputer 조건자 대리자를 사용 하 여 컬렉션의 두 번째 절반에 있는 마지막 컴퓨터 책의 인덱스를 찾습니다.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

설명

Predicate<T>은 전달 된 개체가 대리자에 정의 된 조건과 일치 하는 경우 true를 반환 하는 메서드에 대 한 대리자입니다.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. 현재 List<T>의 요소는 List<T>에서 뒤로 이동 하 여 마지막 요소부터 시작 하 여 첫 번째 요소로 끝나는 Predicate<T> 대리자에 개별적으로 전달 됩니다.The elements of the current List<T> are individually passed to the Predicate<T> delegate, moving backward in the List<T>, starting with the last element and ending with the first element. 일치 하는 경우 처리가 중지 됩니다.Processing is stopped when a match is found.

중요

값 형식이 포함 된 목록을 검색 하는 경우 형식에 대 한 기본값 검색 조건자를 충족 하지 않는 있는지 확인 합니다.When searching a list containing value types, make sure the default value for the type does not satisfy the search predicate. 이 고, 그렇지는 일치가 발견 되지 않았음을 나타내는 기본 값 및 형식에 대해 기본값이 지정 하는 목록 요소를 구분할 수 없으므로가 있습니다.Otherwise, there is no way to distinguish between a default value indicating that no match was found and a list element that happens to have the default value for the type. 기본값이 검색 조건자를 충족 하면 FindLastIndex 메서드를 대신 사용 합니다.If the default value satisfies the search predicate, use the FindLastIndex method instead.

이 메서드는 선형 검색을 수행 합니다. 따라서이 메서드는 O (n) 작업입니다. 여기서 nCount입니다.This method performs a linear search; therefore, this method is an O(n) operation, where n is Count.

적용 대상

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