List<T>.ConvertAll(Converter<T,TOutput>) List<T>.ConvertAll(Converter<T,TOutput>) List<T>.ConvertAll(Converter<T,TOutput>) List<T>.ConvertAll(Converter<T,TOutput>) Method

定義

將目前 List<T> 中的項目轉換成另一個類型,並傳回包含轉換過的項目清單。Converts the elements in the current List<T> to another type, and returns a list containing the converted elements.

public:
generic <typename TOutput>
 System::Collections::Generic::List<TOutput> ^ ConvertAll(Converter<T, TOutput> ^ converter);
public System.Collections.Generic.List<TOutput> ConvertAll<TOutput> (Converter<T,TOutput> converter);
member this.ConvertAll : Converter<'T, 'Output> -> System.Collections.Generic.List<'Output>
Public Function ConvertAll(Of TOutput) (converter As Converter(Of T, TOutput)) As List(Of TOutput)

類型參數

TOutput

目標陣列項目的類型。The type of the elements of the target array.

參數

converter
Converter<T,TOutput>

Converter<TInput,TOutput> 委派,可將某一個類型的每一個項目轉換成另一個類型。A Converter<TInput,TOutput> delegate that converts each element from one type to another type.

傳回

List<TOutput>

目標類型的 List<T>,包含從目前 List<T> 中轉換過的項目。A List<T> of the target type containing the converted elements from the current List<T>.

例外狀況

範例

下列範例會定義名為的方法PointFToPoint以將轉換成PointF結構Point結構。The following example defines a method named PointFToPoint that converts a PointF structure to a Point structure. 這個範例會建立List<T>PointF結構,則會建立Converter\<PointF, Point>委派 (Converter(Of PointF, Point) Visual Basic 中) 來代表PointFToPoint方法,並傳遞至委派ConvertAll方法。The example then creates a List<T> of PointF structures, creates a Converter\<PointF, Point> delegate (Converter(Of PointF, Point) in Visual Basic) to represent the PointFToPoint method, and passes the delegate to the ConvertAll method. ConvertAll方法會傳遞至輸入清單的每個項目PointFToPoint方法並將已轉換的項目放入新的清單Point結構。The ConvertAll method passes each element of the input list to the PointFToPoint method and puts the converted elements into a new list of Point structures. 這兩份清單會顯示。Both lists are displayed.

#using <System.Drawing.dll>

using namespace System;
using namespace System::Drawing;
using namespace System::Collections::Generic;

Point PointFToPoint(PointF pf)
{
    return Point((int) pf.X, (int) pf.Y);
};

void main()
{
    List<PointF>^ lpf = gcnew List<PointF>();

    lpf->Add(PointF(27.8F, 32.62F));
    lpf->Add(PointF(99.3F, 147.273F));
    lpf->Add(PointF(7.5F, 1412.2F));

    Console::WriteLine();
    for each(PointF p in lpf)
    {
        Console::WriteLine(p);
    }

    List<Point>^ lp = 
        lpf->ConvertAll<Point>(
            gcnew Converter<PointF, Point>(PointFToPoint)
        );

    Console::WriteLine();
    for each(Point p in lp)
    {
        Console::WriteLine(p);
    }
}

/* This code example produces the following output:

{X=27.8, Y=32.62}
{X=99.3, Y=147.273}
{X=7.5, Y=1412.2}

{X=27,Y=32}
{X=99,Y=147}
{X=7,Y=1412}
 */
using System;
using System.Drawing;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        List<PointF> lpf = new List<PointF>();

        lpf.Add(new PointF(27.8F, 32.62F));
        lpf.Add(new PointF(99.3F, 147.273F));
        lpf.Add(new PointF(7.5F, 1412.2F));

        Console.WriteLine();
        foreach( PointF p in lpf )
        {
            Console.WriteLine(p);
        }

        List<Point> lp = lpf.ConvertAll( 
            new Converter<PointF, Point>(PointFToPoint));

        Console.WriteLine();
        foreach( Point p in lp )
        {
            Console.WriteLine(p);
        }
    }

    public static Point PointFToPoint(PointF pf)
    {
        return new Point(((int) pf.X), ((int) pf.Y));
    }
}

/* This code example produces the following output:

{X=27.8, Y=32.62}
{X=99.3, Y=147.273}
{X=7.5, Y=1412.2}

{X=27,Y=32}
{X=99,Y=147}
{X=7,Y=1412}
 */
Imports System
Imports System.Drawing
Imports System.Collections.Generic

Public Class Example

    Public Shared Sub Main()

        Dim lpf As New List(Of PointF)

        lpf.Add(New PointF(27.8, 32.62))
        lpf.Add(New PointF(99.3, 147.273))
        lpf.Add(New PointF(7.5, 1412.2))

        Console.WriteLine()
        For Each p As PointF In lpf
            Console.WriteLine(p)
        Next

        Dim lp As List(Of Point) = lpf.ConvertAll( _
            New Converter(Of PointF, Point)(AddressOf PointFToPoint))

        Console.WriteLine()
        For Each p As Point In lp
            Console.WriteLine(p)
        Next

    End Sub

    Public Shared Function PointFToPoint(ByVal pf As PointF) _
        As Point

        Return New Point(CInt(pf.X), CInt(pf.Y))
    End Function
End Class

' This code example produces the following output:
'
'{X=27.8, Y=32.62}
'{X=99.3, Y=147.273}
'{X=7.5, Y=1412.2}
'
'{X=28,Y=33}
'{X=99,Y=147}
'{X=8,Y=1412}

備註

Converter<TInput,TOutput>是將物件轉換成目標型別方法的委派。The Converter<TInput,TOutput> is a delegate to a method that converts an object to the target type. 目前的項目List<T>個別傳遞給Converter<TInput,TOutput>委派,以及已轉換的項目會儲存在新List<T>The elements of the current List<T> are individually passed to the Converter<TInput,TOutput> delegate, and the converted elements are saved in the new List<T>.

目前List<T>會維持不變。The current List<T> remains unchanged.

這個方法是 O (n) 運算,其中nCountThis method is an O(n) operation, where n is Count.

適用於

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