vb.net 克隆列表（类）
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/14467442/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Clone a List(Of Class)
提问by sinDizzy
I've done some reading and cant seem to wrap my head around what the best approach would be to clone a List(of class) in my VB2010 project. I have three classes that are related like so
我已经阅读了一些内容，但似乎无法理解在我的 VB2010 项目中克隆 List（类）的最佳方法是什么。我有三个相关的类
Public Class City
'here are many fields of type string and integer
Public Roads As New List(Of Road)
End Class
Public Class Road
'here are many fields of type string and integer
Public Hazards As New List(Of Hazard)
End Class
Public Class Hazard
Implements ICloneable
'here are many fields of type string and integer and double
Public Function Clone() As Object Implements System.ICloneable.Clone
Return Me.MemberwiseClone
End Function
End Class
So lets say I have a city I'm working on, there are cases where I want to create, as a base one road and its hazards, then add another road but using the prior roads hazards as a starting point and then tweak the fields.
所以假设我有一个我正在研究的城市，在某些情况下，我想创建一条道路及其危险作为基础，然后添加另一条道路，但使用先前的道路危险作为起点，然后调整字段.
Dim rd As New Road
'add road fields
dim hz1 as New Hazard
'add hazard fields
dim hz2 as New Hazard
'add hazard fields
'add the hazard objects to the road
rd.Hazards.Add(hz1)
rd.Hazards.Add(hz2)
'add the road to the city
myCity.Roads.Add(rd)
'here I want to start a new road based on the old road
Dim rdNew As New Road
'copy or clone the hazards from old road
rdNew.Hazards = rd.Hazards '<============
'over-write some of the hazard fields
rdNew.Hazards(0).Description = "temp"
So I know that copying a class will copy the pointer and not the contents. I used the ICloneable interface in the hazard class but cant say I'm using it right. The Hazards variable is a list of Hazard class. How would i go about cloning that class?
所以我知道复制一个类将复制指针而不是内容。我在 hazard 类中使用了 ICloneable 接口，但不能说我用对了。Hazards 变量是 Hazard 类的列表。我将如何克隆该课程？
回答by Guffa
Implementing IClonabledoesn't mean that it replaces the regular assignment, it will still just copy the reference. And you aren't even copying the items, you are copying the list, which means that you still only have one list, but two references to it.
实现IClonable并不意味着它取代了常规赋值，它仍然只是复制引用。而且您甚至没有复制项目，而是复制列表，这意味着您仍然只有一个列表，但有两个引用。
To use the Clonemethod you have to call it for each item in the list:
要使用该Clone方法，您必须为列表中的每个项目调用它：
rdNew.Hazards = rd.Hazards.Select(Function(x) x.Clone()).Cast(Of Hazard).ToList()
回答by Tom
Imports System.IO
Imports System.Xml.Serialization
Public Function CopyList(Of T)(oldList As List(Of T)) As List(Of T)
'Serialize
Dim xmlString As String = ""
Dim string_writer As New StringWriter
Dim xml_serializer As New XmlSerializer(GetType(List(Of T)))
xml_serializer.Serialize(string_writer, oldList)
xmlString = string_writer.ToString()
'Deserialize
Dim string_reader As New StringReader(xmlString)
Dim newList As List(Of T)
newList = DirectCast(xml_serializer.Deserialize(string_reader), List(Of T))
string_reader.Close()
Return newList
End Function
