vb.net - 将对象添加到数组列表
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vb.net - add object to arraylist
提问by Joe
I'm having some trouble adding an object to an arraylist.
我在将对象添加到数组列表时遇到了一些问题。
Basically the object has two properties (file id/name), but I can't figure out how to assign those properties. During runtime it errors out with public member on the object not found.
基本上该对象有两个属性（文件 ID/名称），但我不知道如何分配这些属性。在运行时，它在找不到对象上的公共成员上出错。
Private QueueList As New ArrayList
Public Sub Queue(ByVal FileName As String, ByVal FileID As Integer)
Dim QueueObj As New Object
QueueObj.FileID = "Test 1"
QueueObj.FileName = "Test 2"
QueueList.Add(QueueObj)
End Sub
I'd also like to know how I can do a loop on the arraylist and access the two properites on each record.
我还想知道如何对数组列表进行循环并访问每个记录上的两个属性。
Thanks!
谢谢！
回答by Joel Coehoorn
You can't just use "Object" for this. You need to build your own class:
你不能只使用“对象”。您需要构建自己的类：
Public Class File
Public Property FileID As Integer
Public Property FileName As String
Public Sub New ()
End Sub
Public Sub New(ByVal FileName As String, ByVal FileID As Integer)
Me.FileID = FileID
Me.FileName = FileName
End Sub
End Class
And then build your Queue like this:
然后像这样构建你的队列：
Private QueueList As New ArrayList()
Public Sub Queue(ByVal FileName As String, ByVal FileID As Integer)
QueueList.Add(New File(FileName, FileID))
End Sub
Public Sub Queue(ByVal FileObj As File)
QueueList.Add(FileObj)
End Sub
Or, even better, use generics:
或者，更好的是，使用泛型：
Public QueueList As New List(Of File)()
Public Sub Queue(ByVal FileName As String, ByVal FileID As Integer)
QueueList.Add(New File(FileName, FileID))
End Sub
Public Sub Queue(ByVal FileObj As File)
QueueList.Add(FileObj)
End Sub
Then, to loop over list:
然后，循环遍历列表：
For Each item As File In QueueList
'Console.WriteLine(item.FileID & vbTab & item.FileName)
Next item
回答by asawyer
You need to switch to an object to hold your file information, and drop ArrayList for a strongly typed collection.
您需要切换到一个对象来保存您的文件信息，并为强类型集合删除 ArrayList。
public class QueueFile
public Property FileID as integer
public property FileName as string
end class
...
...
Private QueueList As New List(Of QueueFile)
Public Sub Queue(ByVal FileName As String, ByVal FileID As Integer)
Dim QueueObj As New QueueFile
QueueObj.FileID = "Test 1"
QueueObj.FileName = "Test 2"
QueueList.Add(QueueObj)
End Sub
回答by Jim Wooley
If you only have two values, you may find using a generic Dictionary even better than an ArrayList (requiring boxing and unboxing the types) or List(Of T) which retains type safety.
如果您只有两个值，您可能会发现使用通用 Dictionary 甚至比 ArrayList（需要装箱和拆箱类型）或保留类型安全的 List(Of T) 更好。
Private QueueList As New Dictionary(of Integer, String)
Public Sub Queue(ByVal FileName As String, ByVal FileID As Integer)
QueueList.Add(FileID, FileName)
End Sub
If you really want a Queue as your method name indicates, consider using the generic Queue. Also, if you only need a key/value pair, you don't need to create your own class. You can use the generic KeyValuePair(Of T, S):
如果您真的想要一个 Queue 作为您的方法名称所指示的，请考虑使用通用 Queue。此外，如果您只需要一个键/值对，则不需要创建自己的类。您可以使用通用 KeyValuePair(Of T, S)：
Private QueueItems As New Queue(Of KeyValuePair(Of Integer, String))
Public Sub Queue(ByVal FileName As String, ByVal FileID As Integer)
QueueItems.Enqueue(New KeyValuePair(Of Integer, String)(FileID, FileName))
End Sub
To get items out, use the QueueItems.Dequeue.
要取出项目，请使用 QueueItems.Dequeue。
