我正在编写一个C＃控制台应用程序，它通过TCP连接到服务器并接收定期数据。 我正在使用我在这里找到的一些代码，这是一个很容易使用的异步客户端。 使用它，我的代码启动，建立连接，然后等待事件：
static void Main(string[] args) { agents = new ObservableCollection<AgentState>(); EventDrivenTCPClient client = new EventDrivenTCPClient(IPAddress.Parse("192.168.0.1"), 5000); client.DataReceived += new EventDrivenTCPClient.delDataReceived(client_DataReceived); client.Connect(); do { while (!Console.KeyAvailable) { Thread.Sleep(50); } } while (Console.ReadKey(true).Key != ConsoleKey.Q); client.Disconnect(); }这将启动应用程序，在端口5000上连接到192.168.0.1，然后开始侦听响应。 当它们被收到时，我更新一个名为“clients”的ObservableCollection（由对象“ClientState”组成），结果如下：
static void client_DataReceived(EventDrivenTCPClient sender, object data) { string received = data as string; string parameters=received.Split(','); ClientState thisclient = clients.FirstOrDefault(a => a.clientName == parameters[0]); var index = clients.IndexOf(thisclient); if (index < 0) { ClientState newclient = new ClientState(); newclient.clientName = clientname; newclient.currentState = state; newclient.currentCampaign = campaign; clients.Add(newclient); } else { clients[index].currentState = state; clients[index].currentCampaign = campaign; } }令我惊讶的是，这一切都运行良好：代码很好地收集，收集统计数据并添加和更新ObservableCollection。 然而，问题是当我尝试挂钩到PropertyChanged时...首先，我补充说
clients.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(agents_CollectionChanged);到Main（），然后我添加：
static void clients_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) { foreach (INotifyPropertyChanged item in e.NewItems) item.PropertyChanged += new PropertyChangedEventHandler(newagent_PropertyChanged); }我希望在ObservableCollection发生任何变化时调用newagent_PropertyChanged方法（此时只是吐出到控制台）..但是有些原因，一旦触发了PropertyChanged事件，我就会在“ TCP代码中的cbDataRecievedCallbackComplete“方法：
无法将类型为“ClientState”的对象强制转换为“System.ComponentModel.INotifyPropertyChanged”。
...所以不知何故，尝试引发PropertyChanged的行为导致“cbDataRecievedCallbackComplete”代码触发; 这几乎就像事件是“过路”一样。 如果我“捕获”错误，代码将停止并且不再处理任何传入的数据。
我没有足够的经验知道这是我引入的问题，还是源代码。 我会把钱当作前者：谁能看到哪里有问题所在？
更新：为了回应下面的答案，我已经将我的类定义更改为：
public class ClientState : INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; protected virtual void OnPropertyChanged(string propertyName) { var handler = PropertyChanged; if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName)); } public string agentName { get; set; } public string currentCampaign { get; set; } public string _currentState; public string currentState { get { return _currentState; } set { if (value != _currentState) { _currentState = value; OnPropertyChanged("CurrentState"); } } } }...所以我希望对“currentState”的任何更改都能触发事件。 但是，我在同一个地方收到错误，但现在错误是：
你调用的对象是空的。
在r.DataReceived.EndInvoke(result)行中。
I'm writing a C# console application that connects to a server via TCP and receives periodic data back. I'm using some code I found here, which is a nice easy to use async client. Using this, my code starts up, makes a connection and then waits for events:
static void Main(string[] args) { agents = new ObservableCollection<AgentState>(); EventDrivenTCPClient client = new EventDrivenTCPClient(IPAddress.Parse("192.168.0.1"), 5000); client.DataReceived += new EventDrivenTCPClient.delDataReceived(client_DataReceived); client.Connect(); do { while (!Console.KeyAvailable) { Thread.Sleep(50); } } while (Console.ReadKey(true).Key != ConsoleKey.Q); client.Disconnect(); }This starts up the app, connects to 192.168.0.1 on port 5000 and then starts listening for responses. When they're received, I update an ObservableCollection called "clients" (comprised of object "ClientState") with the results:
static void client_DataReceived(EventDrivenTCPClient sender, object data) { string received = data as string; string parameters=received.Split(','); ClientState thisclient = clients.FirstOrDefault(a => a.clientName == parameters[0]); var index = clients.IndexOf(thisclient); if (index < 0) { ClientState newclient = new ClientState(); newclient.clientName = clientname; newclient.currentState = state; newclient.currentCampaign = campaign; clients.Add(newclient); } else { clients[index].currentState = state; clients[index].currentCampaign = campaign; } }To my great surprise, this all works fine: the code ticks along nicely, collecting the stats and adding to and updating the ObservableCollection. However, the problem is when I try to hook into the PropertyChanged... firstly, I add
clients.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(agents_CollectionChanged);to Main(), then I add:
static void clients_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) { foreach (INotifyPropertyChanged item in e.NewItems) item.PropertyChanged += new PropertyChangedEventHandler(newagent_PropertyChanged); }I'd like this to call the newagent_PropertyChanged method (which just spits out to the Console at the moment) when anything changes in the ObservableCollection .. but some reason, as soon as a PropertyChanged event is fired, I get an exception in the "cbDataRecievedCallbackComplete" method in the TCP code:
Unable to cast object of type 'ClientState' to type 'System.ComponentModel.INotifyPropertyChanged'.
... so somehow, the act of trying to raise a PropertyChanged is causing the "cbDataRecievedCallbackComplete" code to fire; it's almost as if the events are "crossing paths". If I "catch" the error the code grinds to a halt and doesn't process any more incoming data.
I don't have enough experience to know if this is a problem that I've introduced, or with the source code. I'll put money on it being the former: can anyone see where there problem lies?
UPDATE: In response to the answers below, I've changed my class definition to look like:
public class ClientState : INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; protected virtual void OnPropertyChanged(string propertyName) { var handler = PropertyChanged; if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName)); } public string agentName { get; set; } public string currentCampaign { get; set; } public string _currentState; public string currentState { get { return _currentState; } set { if (value != _currentState) { _currentState = value; OnPropertyChanged("CurrentState"); } } } }... so I'd expect any changes to "currentState" to trigger an event. However, I get an error in the same place, except now the error is:
Object reference not set to an instance of an object.
in the r.DataReceived.EndInvoke(result) line of the cbDataRecievedCallbackComplete.
最满意答案
如果ClientState的类定义看起来不像这样
public class ClientState : INotifyPropertyChanged那么你不能把它强制转换为INotifyPropertyChanged类型。 您没有获得编译时异常，因为e.NewItems集合的类型为object，因此它会让您尝试将其强制转换为任何内容。
If your class definition for ClientState doesn't look something like this
public class ClientState : INotifyPropertyChangedthen you cannot cast it to the type INotifyPropertyChanged. You aren't getting a compile time exception because the e.NewItems collection is of type object so it will let you try to cast it to anything.
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