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,当我尝试将 NetworkClient 转换为 SkyfilterClient 时。引发异常,无法将“Network.NetworkClient”类型的对象强制转换为“Network.SkyfilterClient”类型。
我的代码有什么问题吗?我看到Stream可以转换为NetworkStream、MemoryStream。为什么NetworkClient无法转换为Skyfilter Client?
只要该对象实际上是一个SkyfilterClient
,那么演员表应该可以工作。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{}
然而,如果它实际上是一个NetworkClient
,那么你就不能神奇地让它成为子类。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,您可以创建一个转换器类。这里还有一个例子:
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,您无法以这种方式进行转换是有原因的。您可能缺少子类所需的关键信息。
最后,如果您只是想看看尝试的强制转换是否有效,那么您可以使用is
:
if(client is SkyfilterClient)
cast
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