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How to know if it is a reader in a delegate event callback?

I have a question about callback.
I have two forms(VS2010).
I have made a class that raise an event when the ''valueIN'' change.
I set a delegate in my class so that any Form can get the ValueIN when it changes.
The problem
I create the Form2 object and link a callback to it so it is able to get ''valueIN''. but if the form2 object is not instantiated the run time tells me that there is no instantiation of the object.
So I would like to know how do I know that Form2 exists in my WorkingStation.
This line: SetValueINValCallback(value_received);
should looks like something (In workstationlooking at Form2): if(SetValINCallbackFn.exists) SetValueINValCallback(value_received);
Form2
namespace DelegateTest
{
using Beckhoff.App.Ads.Core;
using Beckhoff.App.Ads.Core.Plc;
using TwinCAT.Ads;
using System.IO;
public delegate void DEL_SetValIN(Single value);//test event
public partial class Form1 : Form
{
IBAAdsServer _adsServer;
WorkingStation WorkStation;
public Form1()
{
InitializeComponent();
WorkingStation WorkStation = new WorkingStation(_adsServer);
}
private void btn_Frm2Open_Click(object sender, EventArgs e)
{
Form2 Form2Test = new Form2();
WorkStation.SetValueINValCallback += new DEL_SetValIN(Form2Test.SetValINCallbackFn);
Form2Test.Show();
}
}
}
namespace DelegateTest
{
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
public void SetValINCallbackFn(Single Value_received)//refresh valueIN
{
label1.Text = Value_received.ToString("F1");
}
}
}
WorkStation
namespace DelegateTest
{
using System;
using System.Collections.Generic;
using System.IO;
using System.Windows.Forms;//msgbox
using Beckhoff.App.Ads.Core;
using Beckhoff.App.Ads.Core.Plc;
using TwinCAT.Ads;
public class WorkingStation
{//working station class
public DEL_SetValIN SetValueINValCallback;
private static IBAAdsCncClient _cncClient;
private static IBAAdsPlcClient _plcClient;
public static List<IBAAdsNotification> _notifications;
//no need public event System.EventHandler e_RefreshValueIN;//Input value has changed
public WorkingStation(IBAAdsServer _adsServer) //constructor
{
try
{
_cncClient = _adsServer.GetAdsClient<IBAAdsCncClient>("CNC");
_plcClient = _adsServer.GetAdsClient<IBAAdsPlcClient>("PLC");
_notifications = new List<IBAAdsNotification>();
var _refreshValueIN = new OnChangeDeviceNotification("GlobalVar.PLC.valueInput", ValINHasChanged);//event handler value
_plcClient.AddPlcDeviceNotification(_refreshValueIN);
_notifications.Add(_refreshValueIN);
}
catch (Exception Except)
{ MessageBox.Show("Error init object:" + Except.Message); }
}
~WorkingStation()//destructor
{
foreach (var notify in _notifications)
{
_plcClient.RemovePlcDeviceNotification(notify);
}
}
protected virtual void ValINHasChanged(object sender, BAAdsNotificationItem notification)//get Input value
{//event method
Single value_received = 0;
try
{
value_received = _plcClient.ReadSymbol<Single>("valueInput");
SetValueINValCallback(value_received);
//no need EventHandler E_VIChange = e_RefreshValueIN;
//no need if (E_VIChange != null)
//no need E_VIChange(this, EventArgs.Empty);
}
catch (Exception except)
{
MessageBox.Show("bad event (valueIN): " + except.Message);
}
}
}
}
or does it exist another way to pass event from a class to multiple Forms?
I need those values to draw a chart in Form2 for an example.
Thanks in advance for your help!

Sorry because I didn't see that I was raising an event.
If I've made a delegate is to subscribe to the event, so I don't need to had a raising event, I just need to subscribe.
The error raised because if you code an event like:
protected virtual void ValINHasChanged(object sender, BAAdsNotificationItem notification)//get Input value
{//event method
{
EventHandler E_VIChange = e_RefreshValueIN;
if (E_VIChange != null)
E_VIChange(this, EventArgs.Empty);
}
You need to have a subscriber like
subscriber += new EventHandler... and so on
And you don^t need it anymore because you have the delegate that make the job. so you just have to subscribe to the delegate callback to have your info.
Sorry for the wasting of time.
Best regards

Redirecting Events to handlers inside custom controls

I have mad a custom control. and i need to redirect the Event handler. i have cut the code down dramatically to try and articulate what im trying to do.
public class RemoteDesktop : WindowsFormsHost
{
public event OnConnectingEventHandler OnConnecting;
public delegate void OnConnectingEventHandler(object sender, EventArgs Arguments);
public event OnDisconnectingEventHandler OnDisconnecting;
public delegate void OnDisconnectingEventHandler(Object sender, IMsTscAxEvents_OnDisconnectedEvent Arguments);
private AxMsRdpClient7NotSafeForScripting RDPUserControl = new AxMsRdpClient7NotSafeForScripting();
public RemoteDesktop()
{
this.RDPUserControl.BeginInit();
this.RDPUserControl.SuspendLayout();
base.Child = RDPUserControl;
this.RDPUserControl.ResumeLayout();
this.RDPUserControl.EndInit();
}
}
public class RemoteDesktopViewModel
{
public RemoteDesktopViewModel()
{
RemoteDesktop newRDC = new RemoteDesktop();
newRDC.OnConnecting += new RemoteDesktop.OnConnectingEventHandler(newRDC_OnConnecting);
}
void newRDC_OnConnecting(object sender, EventArgs Arguments)
{
//DoStuff
}
}
basically it all works, i can connect and disconnect to the remote computer however i cannot get the fired events to occur in my view model.
Can anyone help me figure out how i can point my events correctly.
Thank you.
Thanks to some help i have the resolution
Step 1:
Declare delegates outside the class (within the namespace)
Step 2:
Declare the events to be called for the control.
Step 3: use the event handlers of the controls to reise the delegates you created
Completed Code
public delegate void OnConnectingEventHandler(object sender, EventArgs Arguments);
public delegate void OnDisconnectingEventHandler(Object sender,IMsTscAxEvents_OnDisconnectedEvent Arguments);
public class RemoteDesktop : WindowsFormsHost
{
public event OnConnectingEventHandler IsConnecting;
public event OnDisconnectingEventHandler IsDisconnecting;
private AxMsRdpClient7NotSafeForScripting RDPUserControl = new AxMsRdpClient7NotSafeForScripting();
public RemoteDesktop()
{
this.RDPUserControl.BeginInit();
this.RDPUserControl.SuspendLayout();
base.Child = RDPUserControl;
this.RDPUserControl.ResumeLayout();
this.RDPUserControl.EndInit();
RDPUserControl.OnConnecting += RemoteDesktop_OnConnecting;
RDPUserControl.OnDisconnected += RDPUserControl_OnDisconnected;
}
void RDPUserControl_OnDisconnected(object sender, IMsTscAxEvents_OnDisconnectedEvent e)
{
IsDisconnecting(sender, e);
}
void RemoteDesktop_OnConnecting(object sender, EventArgs Arguments)
{
IsConnecting(sender, Arguments);
}
}
public class RemoteDesktopViewModel
{
public RemoteDesktopViewModel()
{
RemoteDesktop newRDC = new RemoteDesktop();
newRDC.IsConnecting += new RemoteDesktop.OnConnectingEventHandler(newRDC_OnConnecting);
}
void newRDC_OnConnecting(object sender, EventArgs Arguments)
{
//DoStuff
}
}

//at the constractor of the class
OnConnecting+=RDC_OnConnecting;
then you can write your logic in method:newRDC_OnConnecting. make sure OnConnectingEventHandler have same method signatures with newRDC_OnConnecting.

How to know when dll events fired

I created a dll contain this event handler:
public void tcp1_Data(object sender, Sockets.DataEventArgs e)
{
Tcp tcp = (Tcp)sender;
response = "Socket Connection" + tcp.Tag.ToString() + " replied : " + e.Data.ToString();
tcp.Close();
}
this will fire when server write some thing in socket connection. so by this, I can read the data on socket.
I used this dll in another project. I want to know in my project (that used dll) exactly when server is writing data on socket connection. as you see in tcp1_Data event, I set result into response variable and in main project (that used dll), I checked this variable polling (if response is not null, it means that this event fired). but Its not what I want. I dont want check this variable all the time.
is there any other way?
I tried this as #ThorstenDittmar said:
my dll project (its name is ClientSample) contain:
TheClassInDLL Class
public class TheClassInDLL
{
public event EventHandler<MyEventArgs> DataEventCalled;
public void tcp1_Data(object sender, Sockets.DataEventArgs e)
{
Tcp tcp = (Tcp)sender;
// Note: LOCAL variable
string myresponse = "Socket Connection" + tcp.Tag.ToString() + " replied : " + e.Data.ToString();
// Call the new event here
if (DataEventCalled != null)
DataEventCalled(this, new MyEventArgs(myresponse));
tcp.Close();
}
// We use this class to pass arguments to the event handler
public class MyEventArgs : EventArgs
{
public MyEventArgs(string response)
{
this.Response = response;
}
public string Response
{
get;
private set;
}
}
}
TCPSample class
public class TCPSample
{
Tcp tcp = new Tcp();
tcp.Data += new System.EventHandler
and in another project that I used above dll:
public partial class Form1 : Form
{
private TheClassInDLL myClass;
ClientSample.TCPSample t = new ClientSample.TCPSample();
public Form1()
{
InitializeComponent();
myClass = new TheClassInDLL();
myClass.DataEventCalled += DataEvent;
}
private void button1_Click(object sender, EventArgs e)
{
t.newTCP();
}
private void DataEvent(object sender, TheClassInDLL.MyEventArgs e)
{
MessageBox.Show(e.Response);
}
}
but It didnt work, DataEvent never happend.
Thanks for any helping...

What you wrote here is an event handler that is called when something happens. There must be a class containing this event handler. Instead of writing a global response variable, declare and invoke another event you can subscribe to from outside that class like this:
public class <TheClassInDLL>
{
public event EventHandler<MyEventArgs> DataEventCalled;
// SNIP: All the other code that leads to tcp1_Data being called
...
// The event handler that's called by some code in the class
public void tcp1_Data(object sender, Dart.Sockets.DataEventArgs e)
{
Tcp tcp = (Tcp)sender;
// Note: LOCAL variable
string myresponse = "Socket Connection" + tcp.Tag.ToString() + " replied : " + e.Data.ToString();
// Call the new event here
if (DataEventCalled != null)
DataEventCalled(this, new MyEventArgs(myresponse));
tcp.Close();
}
// We use this class to pass arguments to the event handler
public class MyEventArgs : EventArgs
{
public MyEventArgs(string response)
{
this.Response = response;
}
public string Response
{
get;
private set;
}
}
}
From the caller, you use it like this:
public class <TheCallingClassOutsideDLL>
{
private <TheClassInDLL> myClass;
public TheCallingClassOutsideDLL()
{
myClass = new TheClassInDLL();
myClass.DataEventCalled += DataEvent;
}
private void DataEvent(object sender, <TheClassInDLL>.MyEventArgs e)
{
Console.WriteLine(e.Response);
}
}
Of course you need to replace <TheClassInDLL> and <TheCallingClassOutsideDLL> with the real class names! Creating additional classes of course doesn't work!

For that you got to define your own event and raise it when needed...
for Example -> In the class where you set the "response" variable define an event
//your custom event
public event EventHandler<CustomEventArgs> MyCustomEvent;
//This will raise your event and notify all who registered
private void RaiseMyCustomEvent(CustomEventArgs e)
{
var handler = MyCustomEvent;
if (handler != null)
{
handler(this, e);
}
}
Maybe you will also need CustomEventArgs (used in the example above)
public class CustomEventArgs : EventArgs
{
public String Message {get;private set;}
public CustomEventArgs(String message){
this.Message = message;
}
}
The class which is using the dll and that wants to get notified needs to register for this event
YourDllClassInstance.MyCustomEvent += OnMyCustomEvent;
public void OnMyCustomEvent(object sender, CustomEventArgs e){
Console.WriteLine("Event received");
}
That means in your dll class you got to do something like the following when you want to raise the event
response = "blablabla";
RaiseMyCustomEvent(new CustomEventArgs(response);
Is that what you where asking for?

How to publish and subscribe to events across different classes

Goal: To change a image on a form when either udp or tcp uses its send method
Problem: I have no idea how to get the event, eventhandler and delegates set up correctly
Send Interface
interface ISendData
{
void Send();
}
Tcp Connection class
//Need some type of delegate??
public class TCPconnection : ISendData
{
void Send()
{
//how invoke/fire a send Event?
}
}
UDP Connection class
//Need some type of delegate??
public class UDPConnection : ISendData
{
void Send()
{
//how invoke/fire a send event?
}
}
the winform which 'should' subscribe to seeing the fired events
public class myForm
{
private DataWatcher datawatcher = new DataWatcher();
private Image statusIndicator = null;
public myform()
{
initComponents();
datawatcher.DataSendActive += new DataWatcherSendHandler(DataSending);
datawatcher.DataSendInactive += new DataWatcherSendHandler(NoDataSending);
}
public void DataSending(object sender, DataWatcherArgs e)
{
statusIndicator = Properties.resources.greenLight;
}
public void NoDataSending(object sender, DataWatcherArgs e)
{
statusIndicator = Properties.resources.redLight;
}
}
The Event/Event handler?? But I really have no Idea what I'm doing here to make this work
public delegate void EventHandler(object sender, EventArgs e);
class DataWatcher
{
public event EventHandler DataSendActive;
public event EventHandler DataSendInactive;
protected virtual void onDataSendActive(System.EventArgs e)
{
if (DataSendActive != null)
{
DataSendActive(this, e);
}
}
protected virtual void onDataSendInactive(System.EventArgs e)
{
if (DataSendInactive != null)
{
DataSendInactive(this, e);
}
}
}

There are many conventions used to do this. Here's my little implementation.
public enum ActivityState
{
Sending,
Receiving,
Idle
}
public interface IDataTransferManager
{
// This event will fire when the activity state changes.
// note that Action<T> is introduced in .NET 3.5
// if you're using .NET 2.0, you can use a delegate.
event Action<ActivityState> DataActivityStateChange;
void Send(byte[] data);
//byte[] Receive();
// ... more methods ... //
}
Now the TcpConnection class will implement this.
public class TcpConnection : IDataTransferManager
{
public event Action<ActivityState> DataActivityStateChange;
public void Send(byte[] data)
{
// we're sending data. fire the change event
FireDataActivityStateChange(ActivityState.Sending);
//TODO: send the data
// we're done sending. Fire the change event
FireDataActivityStateChange(ActivityState.Idle);
}
private void FireDataActivityStateChange(ActivityState state)
{
// helper method, so I don't have to check the event
// to avoid null reference exceptions.
if (DataActivityStateChange != null)
DataActivityStateChange(state);
}
}
Here's the setup for your Form.
class MyForm // :Form
{
IDataTransferManager dataManager;
public MyForm()
{ // here, usually an instance will be passed in,
// so there's only one instance throughout the application.
// let's new up an instance for explanation purposes.
dataManager = new TcpConnection();
dataManager.DataActivityStateChange += (state) =>
{
// NOTE: if you don't like inline,
// you can point this labda to a method.
switch (state)
{
case ActivityState.Sending:
// change the image to the spinning toilet ball
break;
case ActivityState.Receiving:
// change the image to the spinning toilet ball, but reverse :P
break;
case ActivityState.Idle:
// hide it ?
break;
}
};
}
}

Here is a simple example of how you could implement an event for sending and not sending and subscribe to it
public class Connection
{
//Set up an event
public event EventHandler DataSending;
public event EventHandler DataNotSending
//This method will trigger the event for sending
private void OnDataSending()
{
if (DataSending!= null) { DataSending(this, EventArgs.Empty); }
}
//this method will trigger the event for finished sending
private void OnDataNotSending()
{
if (DataNotSending!= null) { DataNotSending(this, EventArgs.Empty); }
}
//This method performs your send logic
public void Send()
{
//Call your method that tells the event to be raised
OnDataSending();
//Then put your send code
OnDataNotSending(); //we're done!
}
}
This is how you use it in a consuming program
public class myForm
{
//This method is the one that sets up the
//instance and subscribes to the event
public myForm()
{
Connection con = new Connection();
con.DataSending += new EventHandler(con_DataSending);
con.DataNotSending += new EventHander(con_DataNotSending);
}
void con_DataSending(object sender, EventArgs e)
{
//Put your subscription logic here.
//Whatever you want to do in response to a send
}
void con_DataNotSending(object sender, EventArgs e)
{
//Put your subscription logic here.
//Respond to it not sending
}
}

How can I bubble events from the Repository through the Service up to the UI?

I have a repository that uses components that report events.
I want to show the reported events in the front end.
This is the repository:
public interface IXmlRepository
{
//irrelevant stuff removed
event EventHandler TraceEventHandler;
}
public class XmlPanelRepository : IXmlRepository
{
public XmlPanelRepository()
{
public event EventHandler TraceEventHandler;
var panelCom = new PanelCom(); // this is a COM object that connects to a device
// when something happens in the COM object it reports it.
panelCom.Trace += panelCom_Trace;
// I want to bubble the trace events up to my UI.
TraceEventHandler += TraceEventHandler_Tracing;
}
private void TraceEventHandler_Tracing(object sender, EventArgs e)
{
// what do I do here?
}
void panelCom_Trace(string message)
{
if (TraceEventHandler!= null) TraceEventHandler.Invoke(this, new EventArgs());
}
}
My UI uses a Service to interface with the repository. The service is defined as:
public interface IXmlConfigurationService
{
//irrelevant stuff removed
event EventHandler TraceEventHandler;
}
public class XmlConfigurationService : IXmlConfigurationService
{
public event EventHandler TraceEventHandler;
public XmlConfigurationService(IXmlRepository configurationRepository)
{
_configurationRepository.TraceEventHandler += ConfigurationRepository_TraceEventHandler;
}
void ConfigurationRepository_TraceEventHandler(object sender, EventArgs e)
{
// this never gets hit.
if (TraceEventHandler != null) TraceEventHandler.Invoke(sender, e);
}
}
If I can get this working, I presume I can follow the same steps to get the UI displaying event reports.
How can I get the Service to report the events that are occurring in the repository?

If I understand correctly, you would need to fulfil your event. This is akin to the Observable fulfilling all listening observers in the Observer Pattern. But for events written like this:
public XmlPanelRepository()
{
public event EventHandler TraceEventHandler;
var panelCom = new PanelCom(); // this is a COM object that connects to a device
// when something happens in the COM object it reports it.
panelCom.Trace += panelCom_Trace;
// I want to bubble the trace events up to my UI.
TraceEventHandler += TraceEventHandler_Tracing;
}
private void TraceEventHandler_Tracing(object sender, EventArgs e)
{
if (TraceEventHandler != null)
{
TraceEventHandler(this, e);
}
}
However, perhaps you should name the event something other than TraceEventHandler because you are now exposing an event (which usually is expressed in the past tense).
It is also worth noting that you can potentially change the event args as you bubble up (if you want to). EventHandler(TEventArgs) can help with this.

You're forgetting to use delegates...
Try something like this:
public interface IXmlRepository
{
//irrelevant stuff removed
event EventHandler TraceEventHandler;
}
public class XmlPanelRepository : IXmlRepository
{
public delegate void EventHandler(string parameter1, string parameter2);
public event EventHandler TraceEventHandler;
public XmlPanelRepository()
{
var panelCom = new PanelCom(); // this is a COM object that connects to a device
// when something happens in the COM object it reports it.
panelCom.Trace += panelCom_Trace;
}
void panelCom_Trace(string message)
{
if (EventHandler != null)
EventHandler("Event was hit, here's the message:", message);
}
}
public interface IXmlConfigurationService
{
//irrelevant stuff removed
}
public class XmlConfigurationService : IXmlConfigurationService
{
public XmlConfigurationService(IXmlRepository configurationRepository)
{
_configurationRepository.TraceEventHandler += ConfigurationRepository_EventHandler;
}
void ConfigurationRepository_EventHandler(string parameter1, string parameter2);)
{
// Do something with your parameters.
Response.Write(parameter1 + parameter2);
}
}