我有一个类,NetworkClient作为基类:
using System.IO;
using System.Net.Sockets;
using System.Threading.Tasks;
namespace Network
{
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class NetworkClient
{
public NetworkClient()
{
tcpClient = new TcpClient();
}
public NetworkClient(TcpClient client)
{
tcpClient = client;
}
public virtual bool IsConnected
{
get;
private set;
}
private StreamWriter writer { get; set; }
private StreamReader reader { get; set; }
private TcpClient tcpClient
{
get;
set;
}
public virtual NetworkServerInfo NetworkServerInfo
{
get;
set;
}
public async virtual void Connect(NetworkServerInfo info)
{
if (tcpClient == null)
{
tcpClient=new TcpClient();
}
await tcpClient.ConnectAsync(info.Address,info.Port);
reader = new StreamReader(tcpClient.GetStream());
writer = new StreamWriter(tcpClient.GetStream());
}
public virtual void Disconnect()
{
tcpClient.Close();
reader.Dispose();
writer.Dispose();
}
public async virtual void Send(string data)
{
await writer.WriteLineAsync(data);
}
public async virtual Task<string> Receive()
{
return await reader.ReadLineAsync();
}
}
}
并且还有一个从NetworkClient派生的子类:
using System.Net;
namespace Network
{
using Data;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class SkyfilterClient : NetworkClient
{
public virtual IPAddress Address
{
get;
set;
}
public virtual int Port
{
get;
set;
}
public virtual string SessionID
{
get;
set;
}
public virtual User UserData
{
get;
set;
}
protected virtual bool Authenticate(string username, string password)
{
throw new System.NotImplementedException();
}
}
}
问题是,当我试图将NetworkClient转换为SkyfilterClient时.抛出异常,无法将类型为"Network.NetworkClient"的对象强制转换为"Network.SkyfilterClient".
我的代码有什么问题？我看到Stream可以转换为NetworkStream,MemoryStream.为什么无法将NetworkClient转换为Skyfilter客户端？
Jus*_*ony 50
只要对象实际上是a SkyfilterClient,那么演员应该可以工作.这是一个人为的例子来证明这一点:
using System;
class Program
{
static void Main()
{
NetworkClient net = new SkyfilterClient();
var sky = (SkyfilterClient)net;
}
}
public class NetworkClient{}
public class SkyfilterClient : NetworkClient{}
但是,如果它实际上是一个NetworkClient,那么你就不能神奇地使它成为子类.这是一个例子:
using System;
class Program
{
static void Main()
{
NetworkClient net = new NetworkClient();
var sky = (SkyfilterClient)net;
}
}
public class NetworkClient{}
public class SkyfilterClient : NetworkClient{}
但是,您可以创建转换器类.这是一个例子,同样:
using System;
class Program
{
static void Main()
{
NetworkClient net = new NetworkClient();
var sky = SkyFilterClient.CopyToSkyfilterClient(net);
}
}
public class NetworkClient
{
public int SomeVal {get;set;}
}
public class SkyfilterClient : NetworkClient
{
public int NewSomeVal {get;set;}
public static SkyfilterClient CopyToSkyfilterClient(NetworkClient networkClient)
{
return new SkyfilterClient{NewSomeVal = networkClient.SomeVal};
}
}
但是,请记住,有一个原因你不能用这种方式转换.您可能缺少子类所需的关键信息.
最后,如果您只想查看尝试的演员是否有效,那么您可以使用is:
if(client is SkyfilterClient)
cast
Hey*_*iko 39
我很惊讶AutoMapper还没有作为答案.
从以前的所有答案可以清楚地看出,你无法进行类型转换.但是,使用AutoMapper,在几行代码中,您可以SkyfilterClient根据现有实例进行实例化NetworkClient.
从本质上讲,您可以将以下内容放在当前正在进行类型转换的位置:
using AutoMapper;
...
// somewhere, your network client was declared
var existingNetworkClient = new NetworkClient();
...
// now we want to type-cast, but we can't, so we instantiate using AutoMapper
AutoMapper.Mapper.CreateMap<NetworkClient, SkyfilterClient>();
var skyfilterObject = AutoMapper.Mapper.Map<SkyfilterClient>(existingNetworkClient);
这是一个完整的例子:
public class Vehicle
{
public int NumWheels { get; set; }
public bool HasMotor { get; set; }
}
public class Car: Vehicle
{
public string Color { get; set; }
public string SteeringColumnStyle { get; set; }
}
public class CarMaker
{
// I am given vehicles that I want to turn into cars...
public List<Car> Convert(List<Vehicle> vehicles)
{
var cars = new List<Car>();
AutoMapper.Mapper.CreateMap<Vehicle, Car>(); // Declare that we want some automagic to happen
foreach (var vehicle in vehicles)
{
var car = AutoMapper.Mapper.Map<Car>(vehicle);
// At this point, the car-specific properties (Color and SteeringColumnStyle) are null, because there are no properties in the Vehicle object to map from.
// However, car's NumWheels and HasMotor properties which exist due to inheritance, are populated by AutoMapper.
cars.Add(car);
}
return cars;
}
}
小智 5
如果您必须而且不介意黑客，则可以让序列化为您完成工作。
给定这些类：
public class ParentObj
{
public string Name { get; set; }
}
public class ChildObj : ParentObj
{
public string Value { get; set; }
}
您可以从父实例创建子实例，如下所示：
var parent = new ParentObj() { Name = "something" };
var serialized = JsonConvert.SerializeObject(parent);
var child = JsonConvert.DeserializeObject<ChildObj>(serialized);
这假设您的对象可以很好地进行序列化，obv。
请注意，这可能会比显式转换器慢。仅此示例需要300毫秒左右的时间。
有几种方法可以做到这一点。然而，这是最简单的方法之一，并且它是可重复使用的。
正在发生的事情是，我们获取父类的所有属性并更新子类上的相同属性。其中，baseObj 是父对象，T 是子类。
public static T ConvertToDerived<T>(object baseObj) where T : new()
{
var derivedObj = new T();
var members = baseObj.GetType().GetMembers();
foreach (var member in members)
{
object val = null;
if (member.MemberType == MemberTypes.Field)
{
val = ((FieldInfo)member).GetValue(baseObj);
((FieldInfo)member).SetValue(derivedObj, val);
}
else if (member.MemberType == MemberTypes.Property)
{
val = ((PropertyInfo)member).GetValue(baseObj);
if (val is IList && val.GetType().IsGenericType)
{
var listType = val.GetType().GetGenericArguments().Single();
var list = (IList)Activator.CreateInstance(typeof(List<>).MakeGenericType(listType));
foreach (var item in (IList)val)
{
list.Add(item);
}
((PropertyInfo)member).SetValue(baseObj, list, null);
}
if (((PropertyInfo)member).CanWrite)
((PropertyInfo)member).SetValue(derivedObj, val);
}
}
return derivedObj;
}
我不认为你可以向下转换一个对象，但是有一种简单的方法可以在盒子之外“向下转换”对象。它不是类型安全的，但它可以工作。首先将对象序列化为json，然后反序列化为子类对象。它的工作原理与在 api 之间传递对象相同。因此，虽然有些人可能会说“这不起作用或不好”，但我认为这正是我们互联网当前的工作方式，所以......为什么不使用这种方法呢？只要参数名称相同，就不需要映射，如果是子类，则参数名称相同。注意：这可能不会复制任何私有字段；如果您有一个带参数的构造函数，则可能还需要对其进行测试以确保没有副作用。
这是我的工具箱：
public static string ConvertToJson<T>(this T obj)
{
return JsonConvert.SerializeObject(obj);
}
public static T ConvertToObject<T>(this string json)
{
if (string.IsNullOrEmpty(json))
{
return Activator.CreateInstance<T>();
}
return JsonConvert.DeserializeObject<T>(json);
}
使用方法如下：
var sfcl = networkClient.ConvertToJson().ConvertToObject<SkyfilterClient>();