Converter<TInput,TOutput> 委托

定义

generic <typename TInput, typename TOutput>
public delegate TOutput Converter(TInput input);

public delegate TOutput Converter<in TInput,out TOutput>(TInput input) where TInput : allows ref struct where TOutput : allows ref struct;

public delegate TOutput Converter<in TInput,out TOutput>(TInput input);

public delegate TOutput Converter<TInput,TOutput>(TInput input);

type Converter<'Input, 'Output> = delegate of 'Input -> 'Output

Public Delegate Function Converter(Of In TInput, Out TOutput)(input As TInput) As TOutput 

Public Delegate Function Converter(Of TInput, TOutput)(input As TInput) As TOutput 

类型参数

参数

返回值

表示 TOutput 已 TInput转换的 。

示例

本部分包含两个代码示例。 第一个示例使用类的方法演示Converter<TInput,TOutput>委托ConvertAll，第二个演示具有Array泛型类方法的ConvertAll委托。List<T>

示例 1

下面的代码示例定义一个将结构转换为PointFToPoint结构PointF的方法Point。 然后，该示例创建一个由 PointF 结构构成的数组，创建一个 Converter<PointF, Point> 委托（Visual Basic 中的 Converter(Of PointF, Point)）来表示 PointFToPoint 方法，并将委托传递给 ConvertAll 方法。 该方法 ConvertAll 将输入列表的每个元素传递给 PointFToPoint 该方法，并将转换后的元素放入结构的新列表中 Point 。 将显示这两个列表。

using System;
using System.Drawing;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        // Create an array of PointF objects.
        PointF[] apf = {
            new PointF(27.8F, 32.62F),
            new PointF(99.3F, 147.273F),
            new PointF(7.5F, 1412.2F) };

        // Display each element in the PointF array.
        Console.WriteLine();
        foreach( PointF p in apf )
            Console.WriteLine(p);

        // Convert each PointF element to a Point object.
        Point[] ap = Array.ConvertAll(apf,
            new Converter<PointF, Point>(PointFToPoint));

        // Display each element in the Point array.
        Console.WriteLine();
        foreach( Point p in ap )
        {
            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.Drawing
Imports System.Collections.Generic

Public Class Example
    Public Shared Sub Main()
        ' Create an array of PointF objects.
        Dim apf() As PointF = { _
            New PointF(27.8, 32.62), _
            New PointF(99.3, 147.273), _
            New PointF(7.5, 1412.2)  }

        ' Display each element in the PointF array.
        Console.WriteLine()
        For Each p As PointF In apf
            Console.WriteLine(p)
        Next
        
        ' Convert each PointF element to a Point object.
        Dim ap() As Point = Array.ConvertAll(apf, _
            New Converter(Of PointF, Point)(AddressOf PointFToPoint))

        ' Display each element in the Point array.
        Console.WriteLine()
        For Each p As Point In ap
            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
' The 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}

示例 2

下面的代码示例定义一个将结构转换为PointFToPoint结构PointF的方法Point。 然后，该示例创建 List<T> 结构的 PointF，创建一个 Converter<PointF, Point> 委托（Visual Basic 中的 Converter(Of PointF, Point)），以表示 PointFToPoint 方法，并将委托传递给 ConvertAll 方法。 该方法 ConvertAll 将输入列表的每个元素传递给 PointFToPoint 该方法，并将转换后的元素放入结构的新列表中 Point 。 将显示这两个列表。

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.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}

注解

类的方法ConvertAll和Array类的方法ConvertAll使用此List<T>委托将集合的每个元素从一种类型转换为另一种类型。