我知道我们应该使用字典而不是哈希表。我找不到克隆字典的方法。即使将其转换为 ICollection 以获取 SyncRoot，我知道这也是不受欢迎的。
我现在正忙着改变它。我是否正确假设没有办法以通用方式实现任何类型的克隆，这就是字典不支持克隆的原因？
【问题讨论】：
标签： .net data-structures
这是我曾经写过的一个快速而肮脏的克隆方法……我认为最初的想法来自 CodeProject。
Imports System.Runtime.Serialization
Imports System.Runtime.Serialization.Formatters.Binary
Public Shared Function Clone(Of T)(ByVal inputObj As T) As T
'creating a Memorystream which works like a temporary storeage '
Using memStrm As New MemoryStream()
'Binary Formatter for serializing the object into memory stream '
Dim binFormatter As New BinaryFormatter(Nothing, New StreamingContext(StreamingContextStates.Clone))
'talks for itself '
binFormatter.Serialize(memStrm, inputObj)
'setting the memorystream to the start of it '
memStrm.Seek(0, SeekOrigin.Begin)
'try to cast the serialized item into our Item '
Try
return DirectCast(binFormatter.Deserialize(memStrm), T)
Catch ex As Exception
Trace.TraceError(ex.Message)
return Nothing
End Try
End Using
End Function
用途：
Dim clonedDict As Dictionary(Of String, String) = Clone(Of Dictionary(Of String, String))(yourOriginalDict)
【讨论】：
使用接受字典的构造函数。看这个例子
var dict = new Dictionary<string, string>();
dict.Add("SO", "StackOverflow");
var secondDict = new Dictionary<string, string>(dict);
dict = null;
Console.WriteLine(secondDict["SO"]);
只是为了好玩.. 您可以使用 LINQ！这是一个更通用的方法。
var secondDict = (from x in dict
select x).ToDictionary(x => x.Key, x => x.Value);
编辑
这应该适用于引用类型，我尝试了以下方法：
internal class User
{
public int Id { get; set; }
public string Name { get; set; }
public User Parent { get; set; }
}
以及上面修改过的代码
var dict = new Dictionary<string, User>();
dict.Add("First", new User
{ Id = 1, Name = "Filip Ekberg", Parent = null });
dict.Add("Second", new User
{ Id = 2, Name = "Test test", Parent = dict["First"] });
var secondDict = (from x in dict
select x).ToDictionary(x => x.Key, x => x.Value);
dict.Clear();
dict = null;
Console.WriteLine(secondDict["First"].Name);
输出“Filip Ekberg”。
【讨论】：
IDictionary 的IEqualityComparer，即如果您有一个IDictionary 和StringComparer.OrdinalIgnoreCase。
dict["First"].Name 并且它也将在 secondDict["First"].Name 中更改。从一个集合中删除它与修改它不同。另外，如果你要使用 Linq：只需 dict.ToDictionary 而不是 (from x in dict select x).ToDictionary。
只是因为任何人都需要 vb.net 版本
Dim dictionaryCloned As Dictionary(Of String, String)
dictionaryCloned = (From x In originalDictionary Select x).ToDictionary(Function(p) p.Key, Function(p) p.Value)
【讨论】：
对于原始类型字典
Public Sub runIntDictionary()
Dim myIntegerDict As New Dictionary(Of Integer, Integer) From {{0, 0}, {1, 1}, {2, 2}}
Dim cloneIntegerDict As New Dictionary(Of Integer, Integer)
cloneIntegerDict = myIntegerDict.Select(Function(x) x.Key).ToList().ToDictionary(Of Integer, Integer)(Function(x) x, Function(y) myIntegerDict(y))
End Sub
对于实现 ICloneable 的 Object 的字典
Public Sub runObjectDictionary()
Dim myDict As New Dictionary(Of Integer, number) From {{3, New number(3)}, {4, New number(4)}, {5, New number(5)}}
Dim cloneDict As New Dictionary(Of Integer, number)
cloneDict = myDict.Select(Function(x) x.Key).ToList().ToDictionary(Of Integer, number)(Function(x) x, Function(y) myDict(y).Clone)
End Sub
Public Class number
Implements ICloneable
Sub New()
End Sub
Sub New(ByVal newNumber As Integer)
nr = newnumber
End Sub
Public nr As Integer
Public Function Clone() As Object Implements ICloneable.Clone
Return New number With {.nr = nr}
End Function
Public Overrides Function ToString() As String
Return nr.ToString
End Function
End Class
【讨论】：
对于简单的字典
public static Dictionary<string, object> DictionaryClone(Dictionary<string, object> _Datas)
{
Dictionary<string, object> output = new Dictionary<string, object>();
if (_Datas != null)
{
foreach (var item in _Datas)
output.Add(item.Key, item.Value);
}
return output;
}
【讨论】：