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PointFToPoint的方法, PointF將結構轉換為Point結構。The following example defines a method named PointFToPoint that converts a PointF structure to a Point structure. 然後, 此範例會List<T>建立PointF結構的, Converter\<PointF, Point>建立PointFToPoint委派 (Converter(Of PointF, Point)在 Visual Basic 中) ConvertAll來代表方法, 並將委派傳遞至方法。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. 方法會將輸入清單的每個元素傳遞PointFToPoint至方法, 並將已轉換的元素放入新Point的結構清單。 ConvertAllThe 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. 這兩個清單都會顯示。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之方法的委派。The Converter<TInput,TOutput> is a delegate to a method that converts an object to the target type. 目前List<T>的專案會個別傳遞Converter<TInput,TOutput>至委派, 而已轉換的元素會儲存在新List<T>的中。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>的保持不變。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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