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如何：建立集合初始設定式所使用的集合 (Visual Basic)

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當您使用集合初始設定式來建立集合時，Visual Basic 編譯器會搜尋集合類型的 Add 方法，其中 Add 方法的參數符合集合初始設定式中值的類型。 這個 Add 方法可用來將集合初始設定式中的值填入集合。

範例

下列範例顯示 OrderCollection 集合，其中包含集合初始設定式可用來新增 Add 類型之物件的公用 Order 方法。 Add 方法可讓您使用縮短的集合初始設定式語法。

Public Class Customer
    Public Property Id As Integer
    Public Property Name As String
    Public Property Orders As OrderCollection

    Public Sub New(ByVal id As Integer, ByVal name As String, ByVal orders As OrderCollection)
        Me.Id = id
        Me.Name = name
        Me.Orders = orders
    End Sub
End Class

Public Class Order
    Public Property Id As Integer
    Public Property CustomerId As Integer
    Public Property OrderDate As DateTime

    Public Sub New(ByVal id As Integer,
                   ByVal customerId As Integer,
                   ByVal orderDate As DateTime)
        Me.Id = id
        Me.CustomerId = customerId
        Me.OrderDate = orderDate
    End Sub
End Class

Public Class OrderCollection
    Implements IEnumerable(Of Order)

    Dim items As New List(Of Order)

    Public Property Item(ByVal index As Integer) As Order
        Get
            Return CType(Me(index), Order)
        End Get
        Set(ByVal value As Order)
            items(index) = value
        End Set
    End Property

    Public Sub Add(ByVal id As Integer, ByVal customerID As Integer, ByVal orderDate As DateTime)
        items.Add(New Order(id, customerID, orderDate))
    End Sub

    Public Function GetEnumerator() As IEnumerator(Of Order) Implements IEnumerable(Of Order).GetEnumerator
        Return items.GetEnumerator()
    End Function

    Public Function GetEnumerator1() As IEnumerator Implements IEnumerable.GetEnumerator
        Return Me.GetEnumerator()
    End Function
End Class

Imports System.Runtime.CompilerServices

Module Module1

    <Extension()>
    Sub Add(ByVal genericList As List(Of Customer),
            ByVal id As Integer,
            ByVal name As String,
            ByVal orders As OrderCollection)

        genericList.Add(New Customer(id, name, orders))
    End Sub
End Module

Dim customerList = New List(Of Customer) From
  {
    {1, "John Rodman", New OrderCollection From {{9, 1, #6/12/2008#},
                                                 {8, 1, #6/11/2008#},
                                                 {5, 1, #5/1/2008#}}},
    {2, "Ariane Berthier", New OrderCollection From {{2, 2, #1/18/2008#},
                                                     {4, 2, #3/8/2008#},
                                                     {6, 2, #3/18/2008#},
                                                     {7, 2, #5/14/2008#},
                                                     {5, 2, #4/4/2008#}}},
     {3, "Brian Perry", New OrderCollection From {{1, 3, #1/15/2008#},
                                                  {3, 3, #3/8/2008#}}}
  }

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