Question

我有第三方方法返回旧式ArrayList，我想将其转换为类型化ArrayList（Of MyType）。

Dim udc As ArrayList = ThirdPartyClass.GetValues()
Dim udcT AS List(Of MyType) = ??

我做了一个简单的循环，但必须有一个更好的方法：

Dim udcT As New List(Of MyType)
While udc.GetEnumerator.MoveNext
    Dim e As MyType = DirectCast(udc.GetEnumerator.Current, MyType)
    udcT.Add(e)
End While

Answer 1

Dim StronglyTypedList = OriginalArrayList.Cast(Of MyType)().ToList()
' requires `Imports System.Linq`

Answer 2

重复。看一下这个SO-Thread：In .Net, how do you convert an ArrayList to a strongly typed generic list without using a foreach?

在VB.Net with Framework＆lt; 3.5：

Dim arrayOfMyType() As MyType = DirectCast(al.ToArray(GetType(MyType)), MyType())
Dim strongTypeList As New List(Of MyType)(arrayOfMyType)

Answer 3

这个怎么样？

Public Class Utility

    Public Shared Function ToTypedList(Of C As {ICollection(Of T), New}, T)(ByVal list As ArrayList) As C

        Dim typedList As New C
        For Each element As T In list
            typedList.Add(element)
        Next

        Return typedList
    End Function

End Class

如果适用于任何Collection对象。

Answer 4

I would like to point out something about both the DirectCast and System.Linq.Cast (which are the same thing in the latest .NET at least.) These may not work if the object type in the array is defined by the user class, and is not easily convertable into object types that .NET recognizes. I do not know why this is the case, but it seems to be the problem in the software for which I am developing, and so for these we have been forced to use the inelegant loop solution.

VB.NET ArrayList to List（Of T）类型的复制/转换

4 个答案: