Here is my problem:
In my WPF application I have a MyBaseControl (derives from System.Windows.Controls.ContentControls) and a lot of MyCustomControls which derives from MyBaseControl. I need to do some storing and cleanup operations for all my MyCustomControls befor the application is closed.
Here is some code:
public abstract class MyBaseControl : ContentControl
{
// Do some smart stuff.
}
App.Exit += new System.Windows.ExitEventHandler(App.App_OnExit);
In App_OnExit() I do the really last operations that need to be done.
I tried to do my cleanup operations in the destructor of MyBaseControl but this is called after App_OnExit(). Same problem with AppDomain.CurrentDomain.ProcessExit.
The ContentControl.Closed and ContentControl.Unloaded events don't occour when I exit the application via ALT+F4.
Where can I hook in to do my cleanup operations?
Where can I hook in to do my cleanup operations?
In a Closing event handler for the parent window of the control:
public abstract class MyBaseControl : ContentControl
{
public MyBaseControl()
{
Loaded += MyBaseControl_Loaded;
}
private void MyBaseControl_Loaded(object sender, RoutedEventArgs e)
{
Window parentWindow = Window.GetWindow(this);
parentWindow.Closing += ParentWindow_Closing;
Loaded -= MyBaseControl_Loaded;
}
private void ParentWindow_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
//cleanup...
}
}
You can put it to your application class:
public delegate void TimeToCleanUpEventHandler();
public event TimeToCleanUpEventHandler TimeToCleanUp;
modify Exit event handler:
App.Current.Exit += ((o, e) => { TimeToCleanUp?.Invoke(); App.App_OnExit(o, e); });
and modify your base control:
public abstract class MyBaseControl : ContentControl
{
public MyBaseControl()
{
(App.Current as MyApp).TimeToCleanUp += CleanItUp;
}
public virtual void CleanItUp()
{
(App.Current as MyApp).TimeToCleanUp -= CleanItUp;
//do stuff;
}
}
Related
Short version
In my abstract class MyCbo_Abstract (derived from ComboBox class), I want to create a custom property that when set will subtract all the control's event handlers, set the base property value, then re-add all the control's event handlers.
What I have so far
I have a concrete ComboBox class derived from an abstract ComboBox class derived from Microsoft's ComboBox class.
public abstract class MyCbo_Abstract : ComboBox
{
public MyCbo_Abstract() : base()
{
}
}
public partial class MyCboFooList : MyCbo_Abstract
{
public MyCboFooList() : base()
{
}
}
My main Form class subscribes to certain base ComboBox events.
Note: The designer has: this.myCboFooList = new MyCboFooList();
public partial class FormMain : Form
{
public FormMain()
{
myCboFooList.SelectedIndexChanged += myCboFooList_SelectedIndexChanged;
}
private void myCboFooList_SelectedIndexChanged(object sender, EventArgs e)
{
// do stuff
}
}
There are times when I want to suppress the invocation of defined event handlers, e.g., when I programmatically set a ComboBox object's SelectedIndex property.
Instead of having to remember to write the code to subtract and re-add event handlers each time I want to modify the SelectedIndex property and suppress its events, I want to create a custom property SelectedIndex_NoEvents that when set will subtract all the control's event handlers, set the base property value SelectedIndex, then re-add all the control's event handlers.
The problem
My problem is that I don't know how to iterate over a EventHandlerList because it has no GetEnumerator. And, in looking at the list in the debugger, saveEventHandlerList is a weird chained thing that I can't figure out how to otherwise traverse.
public abstract class MyCbo_Abstract : ComboBox
{
int selectedIndex_NoEvents;
public int SelectedIndex_NoEvents
{
get
{
return base.SelectedIndex;
}
set
{
EventHandlerList saveEventHandlerList = new EventHandlerList();
saveEventHandlerList = Events;
//foreach won't work - no GetEnumerator available. Can't use for loop - no Count poprerty
foreach (EventHandler eventHandler in saveEventHandlerList)
{
SelectedIndexChanged -= eventHandler;
}
base.SelectedIndex = value;
//foreach won't work - no GetEnumerator available. Can't use for loop - no Count poprerty
foreach (EventHandler eventHandler in saveEventHandlerList)
{
SelectedIndexChanged += eventHandler;
}
saveEventHandlerList = null;
}
}
//Probably don't need this
public override int SelectedIndex
{
get
{
return base.SelectedIndex;
}
set
{
base.SelectedIndex = value;
}
}
public DRT_ComboBox_Abstract() : base()
{
}
}
Before giving you the solution that I created, let me say that this feels extremely hacky. I urge you to seriously think about another solution. There may be all kinds of crazy edge cases where this code breaks down, I haven't thoroughly tested it beyond the example code shown below.
Add the following utility class:
public class SuspendedEvents
{
private Dictionary<FieldInfo, Delegate> handlers = new Dictionary<System.Reflection.FieldInfo, System.Delegate>();
private object source;
public SuspendedEvents(object obj)
{
source = obj;
var fields = obj.GetType().GetFields(BindingFlags.Static | BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public);
foreach (var fieldInfo in fields.Where(fi => fi.FieldType.IsSubclassOf(typeof(Delegate))))
{
var d = (Delegate)fieldInfo.GetValue(obj);
handlers.Add(fieldInfo, (Delegate)d.Clone());
fieldInfo.SetValue(obj, null);
}
}
public void Restore()
{
foreach (var storedHandler in handlers)
{
storedHandler.Key.SetValue(source, storedHandler.Value);
}
}
}
You can use it like this:
var events = new SuspendedEvents(obj); //all event handlers on obj are now detached
events.Restore(); // event handlers on obj are now restored.
I used the following test setup:
void Main()
{
var obj = new TestObject();
obj.Event1 += (sender, e) => Handler("Event 1");
obj.Event1 += (sender, e) => Handler("Event 1");
obj.Event2 += (sender, e) => Handler("Event 2");
obj.Event2 += (sender, e) => Handler("Event 2");
obj.Event3 += (sender, e) => Handler("Event 3");
obj.Event3 += (sender, e) => Handler("Event 3");
Debug.WriteLine("Prove events are attached");
obj.RaiseEvents();
var events = new SuspendedEvents(obj);
Debug.WriteLine("Prove events are detached");
obj.RaiseEvents();
events.Restore();
Debug.WriteLine("Prove events are reattached");
obj.RaiseEvents();
}
public void Handler(string message)
{
Debug.WriteLine(message);
}
public class TestObject
{
public event EventHandler<EventArgs> Event1;
public event EventHandler<EventArgs> Event2;
public event EventHandler<EventArgs> Event3;
public void RaiseEvents()
{
Event1?.Invoke(this, EventArgs.Empty);
Event2?.Invoke(this, EventArgs.Empty);
Event3?.Invoke(this, EventArgs.Empty);
}
}
It produces the following output:
Prove events are attached
Event 1
Event 1
Event 2
Event 2
Event 3
Event 3
Prove events are detached
Prove events are reattached
Event 1
Event 1
Event 2
Event 2
Event 3
Event 3
There is no way to easily disable event firing of WinForm controls exposed in the .Net framework. However, the Winform controls follow a standard design pattern for events in that all event signatures are based on the EventHandler Delegate and the registered event handlers are stored in an EventHandlerList that is defined in the Control Class. This list is stored in a field (variable) named "events" and is only publicly exposed via the read-only property Events.
The class presented below uses reflection to temporarily assign null to the events field effectively removing all event handlers registered for the Control.
While it may be an abuse of the pattern, the class implements the IDisposable Interface to restore the events field on disposal of the class instance. The reason for this is to facilitate the use of the using block to wrap the class usage.
public class ControlEventSuspender : IDisposable
{
private const string eventsFieldName = "events";
private const string headFieldName = "head";
private static System.Reflection.FieldInfo eventsFieldInfo;
private static System.Reflection.FieldInfo headFieldInfo;
private System.Windows.Forms.Control target;
private object eventHandlerList;
private bool disposedValue;
static ControlEventSuspender()
{
Type compType = typeof(System.ComponentModel.Component);
eventsFieldInfo = compType.GetField(eventsFieldName, System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
headFieldInfo = typeof(System.ComponentModel.EventHandlerList).GetField(headFieldName, System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
}
private static bool FieldInfosAquired()
{
if (eventsFieldInfo == null)
{
throw new Exception($"{typeof(ControlEventSuspender).Name} could not find the field '{ControlEventSuspender.eventsFieldName}' on type Component.");
}
if (headFieldInfo == null)
{
throw new Exception($"{typeof(ControlEventSuspender).Name} could not find the field '{ControlEventSuspender.headFieldName}' on type System.ComponentModel.EventHandlerList.");
}
return true;
}
private ControlEventSuspender(System.Windows.Forms.Control target) // Force using the the Suspend method to create an instance
{
this.target = target;
this.eventHandlerList = eventsFieldInfo.GetValue(target); // backup event hander list
eventsFieldInfo.SetValue(target, null); // clear event handler list
}
public static ControlEventSuspender Suspend(System.Windows.Forms.Control target)
{
ControlEventSuspender ret = null;
if (FieldInfosAquired() && target != null)
{
ret = new ControlEventSuspender(target);
}
return ret;
}
protected virtual void Dispose(bool disposing)
{
if (!this.disposedValue)
{
if (disposing)
{
if (this.target != null)
{
RestoreEventList();
}
}
}
this.disposedValue = true;
}
public void Dispose()
{
Dispose(true);
}
private void RestoreEventList()
{
object o = eventsFieldInfo.GetValue(target);
if (o != null && headFieldInfo.GetValue(o) != null)
{
throw new Exception($"Events on {target.GetType().Name} (local name: {target.Name}) added while event handling suspended.");
}
else
{
eventsFieldInfo.SetValue(target, eventHandlerList);
eventHandlerList = null;
target = null;
}
}
}
Example usage in the button1_Click method:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
using (ControlEventSuspender.Suspend(comboBox1))
{
comboBox1.SelectedIndex = 3; // SelectedIndexChanged does not fire
}
}
private void button2_Click(object sender, EventArgs e)
{
comboBox1.SelectedIndex = -1; // clear selection, SelectedIndexChanged fires
}
private void button3_Click(object sender, EventArgs e)
{
comboBox1.SelectedIndex = 3; // SelectedIndexChanged fires
}
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
Console.WriteLine("index changed fired");
System.Media.SystemSounds.Beep.Play();
}
}
SoapBox Diatribe
Many will say that the use of Reflection to access non-public class members is dirty or some other derogatory term and that it introduces a brittleness to the code as someone may change the underlying code definition such that the code that relies on member names (magic strings) is no longer valid. This is a valid concern, but I view it as no different than code that accesses external databases.
Reflection can be thought of a query of a type (datatable) from an assembly (database) for specific fields (members: fields, properties, events). It is no more brittle than a SQL statement such as Select SomeField From SomeTable Where AnotherField=5. This type of SQL code is prevent in the world and no one thinks twice about writing it, but some external force could easily redefine the database you code relies on an render all the magic string SQL statements invalid as well.
Use of hard coded names is always at risk of being made invalid by change. You have to weigh the risks of moving forward versus the option of being frozen in fear of proceeding because someone wants to sound authoritative (typically a parroting of other such individuals) and criticize you for implementing a solution that solves the current problem.
I was hoping to write code that would programatically locate all event handler method names created using controlObject.Event += EventHandlerMethodName, but as you see in the other answers, code to do this is complicated, limited, and perhaps not able to work in all cases
This is what I came up with. It satisfies my desire to consolidate the code that subtracts and re-adds event handler method names into my abstract class, but at the expense of having to write code to store and manage event handler method names and having to write code for each control property where I want to suppress the event handler, modify the property value, and finally re-add the event handler.
public abstract class MyCbo_Abstract : ComboBox
{
// create an event handler property for each event the app has custom code for
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
private EventHandler evSelectedValueChanged;
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public EventHandler EvSelectedValueChanged { get => evSelectedValueChanged; set => evSelectedValueChanged = value; }
public MyCbo_Abstract() : base()
{
}
// Create a property that parallels the one that would normally be set in the main body of the program
public object _DataSource_NoEvents
{
get
{
return base.DataSource;
}
set
{
SelectedValueChanged -= EvSelectedValueChanged;
if (value == null)
{
base.DataSource = null;
SelectedValueChanged += EvSelectedValueChanged;
return;
}
string valueTypeName = value.GetType().Name;
if (valueTypeName == "Int32")
{
base.DataSource = null;
SelectedValueChanged += EvSelectedValueChanged;
return;
}
//assume StringCollection
base.DataSource = value;
SelectedValueChanged += EvSelectedValueChanged;
return;
}
}
}
public partial class MyCboFooList : MyCbo_Abstract
{
public MyCboFooList() : base()
{
}
}
Designer has
this.myCboFooList = new MyCboFooList();
Main form code
public partial class FormMain : Form
{
public FormMain()
{
myCboFooList.SelectedValueChanged += OnMyCboFooList_SelectedValueChanged;
myCboFooList.EvSelectedValueChanged = OnMyCboFooList_SelectedValueChanged;
}
private void OnMyCboFooList_SelectedValueChanged(object sender, EventArgs e)
{
// do stuff
}
}
And now, if I want to set a property and suppress event(s), I can write something like the following and not have to remember to re-add the event handler method name
myCboFooList._DataSource_NoEvents = null;
I need to Raise an Event from another Class - i know that this is not possible - but I need a workaround for this.
For now Im doing the following
This is the class, which have to raise the event
internal class DataTransfer
{
public delegate void EventHandler(object sender, OnReaderCommonEventArgs e);
public event EventHandler _OnSerialNumber;
public event EventHandler _OnReaderType
Task DataHandler()
{
//Recieving-Data and Stuff
_OnSerialNumber(this, new OnReaderCommonEventArgs { SerialNumber = RFIDParser.ParseSerialNumber(data) });
_OnReaderType(this, new OnReaderCommonEventArgs { ReaderType = RFIDParser.ParseReaderType(data) });
}
}
And in the Main-Class, which will be used by the user. So the user can only subscribe to the event from this class-object:
public partial class PUR_100U
{
public delegate void EventHandler(object sender, OnReaderCommonEventArgs e);
public event EventHandler OnSerialNumber;
public event EventHandler OnReaderType;
public PUR_100U(int portnumber)
{
dataTransfer = new DataTransfer(portnumber, GetIdentifierList());
dataTransfer._OnSerialNumber += dataTransfer__OnSerialNumber;
dataTransfer._OnReaderType += dataTransfer__OnReaderType;
}
void dataTransfer__OnSerialNumber(object sender, OnReaderCommonEventArgs e)
{
if (OnSerialNumber != null) { OnSerialNumber(this, new OnReaderCommonEventArgs { SerialNumber = e.SerialNumber }); }
}
void dataTransfer__OnReaderType(object sender, OnReaderCommonEventArgs e)
{
if (OnReaderType != null) { OnReaderType(this, new OnReaderCommonEventArgs { ReaderType = e.ReaderType }); }
}
}
Example of user-usage:
rfid = new PUR_100U(20);
rfid.OnSerialNumber += rfid_OnSerialNumber;
rfid.OnReaderType += rfid_OnReaderType;
Is there a better way of doing this?
I need to Raise an Event from another Class - i know that this is not possible - but I need a workaround for this.
That is rather trivial:
class Foo
{
public event EventHandler Fooed; //note, name is not OnFoo
public void FireFooed() => Fooed?.Invoke(this, new EventArgs);
}
And now, fire the event at will:
var foo = new Foo();
foo.FireFooed();
The question is, why do you want to do this? It seems like a really bad idea. Fooed should fire only and only if the preconditions inside Foo for it to fire are met; if you need Fooed to fire, then make the preconditions happen!
Firing Fooed at will if the conditions aren't met will break all other listeners, don't do that.
It's known that there are some solutions similar to this one, but I can't solve my problem with them.
I have two user controls:
The first one makes a Report object.
The second one shows it.
I have a main Form that links both controls.
These two controls are created in a DLL, and are added to the
main form like this:
//ADDS THE FIRST CONTROL TO THE PANEL CONTROL
myDll.controlUserReport userControlA = new myDll.controlUserReport();
panelControl1.Controls.Add(userControlA);
userControlA.Dock = DockStyle.Left;
//ADDS THE SECOND CONTROL TO THE PANEL CONTROL
myDll.controlDocViewer userControlB = new myDll.controlDocViewer();
panelControl1.Controls.Add(userControlB);
userControlB.Dock = DockStyle.Fill;
How can I pass the Report object, which is created in the first control controlUserReport when I click over a button, to the other user control controlDocViewer to show it?
You should use events for this. In UserControlA declare the event:
//Declare EventHandler outside of class
public delegate void MyEventHandler(object source, Report r);
public class UserControlA
{
public event MyEventHandler OnShowReport;
private void btnShowReport_Click(object sender, Report r)
{
OnShowReport?.Invoke(this, this.Report);
}
}
In UserControlB subscribe to the event and show the report:
public class UserControlB
{
// Do it in Form_Load or so ...
private void init()
{
userControlA.OnShowReport += userControlA_OnShowReport;
}
private void userControlA_OnShowReport(object sender, Report r)
{
// Show the report
this.ShowReport(r);
}
}
the post above is good except init() method should not be in ControlB, but in the parent form, something like this:
public class frmMain : Form
{
private void frmMain_Load(object sender, EventArgs e)
{
// subscribe/glue
userControlA.OnShowReport += userControlB.OnShowReport;
userControlB.OnShowReport += userControlA.OnShowReport;
}
public class UserControlA
{
public event EventHandlerNodeCopy OnDataCopy;
public TreeNode NodeCopied { get; set; }
private void some_method(string z, TreeNode trn)
{
OnDataCopy?.Invoke(this, trn);
...
}
public void frmJsTree_OnDataCopy(object source, TreeNode tn)
{
NodeCopied = tn;
}
public class UserControlB
{
public event EventHandlerNodeCopy OnDataCopy;
public TreeNode NodeCopied { get; set; }
private void another_method(int i, TreeNode trn)
{
OnDataCopy?.Invoke(this, trn);
...
}
public void frmJsTree_OnDataCopy(object source, TreeNode tn)
{
NodeCopied = tn;
}
enter code here
Another approach is using BehaviorSubject (requires System.Reactive). Once the data is added in the BehaviorSubject, all places that subscribe can see the info. A very basic example:
Create a class to represent your data. Ex:
DataService.cs
public static BehaviorSubject<YourDataType> MyAwesomeData { get; } = new BehaviorSubject<YourDataType> (null);
In You UserControlA (maybe in the clickEvent from the button) or whatever:
private void btnShowReport_Click(object sender, MouseButtonEventArgs e)
{
// Do some stuffs to prepare the data...
YourDataType myDataReportPrepared = null; // something;
// Here you update your DataInfo on BehaviorSubject
DataService.MyAwesomeData.OnNext(myDataReportPrepared);
}
Finally every place in your solution that uses subscribe in that Subject will listen to that data, like for example in your UserControlB:
// This will trigger every time MyAwesomeData.OnNext() is executed.
DataService.MyAwesomeData.Subscribe(item =>
{
if (item != null){
// Do something with it...Like populate some Datagrid...
}
});
I have 'BasePage' class which is base class for all other pages in my project.
In initialization, I'm adding EventHandler for 'SystemNavigationManager' for event 'BackRequest'. For some reason that line id causing 'AccessViolationException' when XAML designer is trying to render XAML of class that extends 'BasePage'
I'm not familiar with UWP, so I'll be very grateful for tips.
BasePage
public class BasePage: Page {
internal string title = "";
internal HeaderView headerView;
public BasePage() {
this.Loaded += BasePage_Loaded;
// FIXME: For some reason if this line is uncommented then xaml designer fails.
SystemNavigationManager.GetForCurrentView().BackRequested += BasePage_BackRequested;
}
private void BasePage_BackRequested(object sender, BackRequestedEventArgs e) {
bool handled = e.Handled;
this.BackRequested(ref handled);
e.Handled = handled;
}
private void BackRequested(ref bool handled) {
//Get a hold of the current frame so that we can inspect the app back stack.
if (this.Frame == null)
return;
// Check to see if this is the top-most page on the app back stack.
if (this.Frame.CanGoBack && !handled) {
// If not, set the event to handled and go back to the previous page in the app.
handled = true;
this.Frame.GoBack();
}
}
private void setupPageAnimation() {
TransitionCollection collection = new TransitionCollection();
NavigationThemeTransition theme = new NavigationThemeTransition();
var info = new ContinuumNavigationTransitionInfo();
theme.DefaultNavigationTransitionInfo = info;
collection.Add(theme);
this.Transitions = collection;
}
private void BasePage_Loaded(object sender, Windows.UI.Xaml.RoutedEventArgs e) {
setupPageAnimation();
}
}
SOLUTION
Just like Ivan said, final code looks like this. Without of a trace of bug.
BasePage
public BasePage() {
this.Loaded += BasePage_Loaded;
}
protected override void OnNavigatedTo(NavigationEventArgs e) {
base.OnNavigatedTo(e);
SystemNavigationManager.GetForCurrentView().BackRequested += BasePage_BackRequested;
}
protected override void OnNavigatedFrom(NavigationEventArgs e) {
base.OnNavigatedFrom(e);
SystemNavigationManager.GetForCurrentView().BackRequested -= BasePage_BackRequested;
}
You shouldn't subscribe to back events on constructor but OnNavigatedTo and unsubscribe in OnNavigatedFrom. Even if it didn't crash it would cause a lot of problems because your back logic would be activated on all previous pages when you press the back button.
Please forgive my little knowledge!
I have the following class in HIDNewDeviceEventMonitor.cs:
public class HIDNewDeviceEventMonitor : IDisposable
{
// used for monitoring plugging and unplugging of USB devices.
private ManagementEventWatcher watcherAttach;
public HIDNewDeviceEventMonitor()
{
// Catch USB HID plugged instance event watching
watcherAttach = new ManagementEventWatcher();
watcherAttach.EventArrived += new EventArrivedEventHandler(watcher_EventArrived);
watcherAttach.Query = new WqlEventQuery(#"SELECT * FROM __InstanceCreationEvent WITHIN 2 WHERE TargetInstance ISA 'Win32_PNPEntity' AND TargetInstance.DeviceID LIKE 'HID\\VID_04D8%'");
watcherAttach.Start();
}
void watcher_EventArrived(object sender, EventArrivedEventArgs e)
{
Debug.WriteLine("my device is inserted..");
}
public void Dispose()
{
watcherAttach.Stop();
watcherAttach.Dispose();
}
~HIDNewDeviceEventMonitor()
{
this.Dispose();
}
}
Now, how can I change this class to be able to add an event handler that the class can call from within watcher_EventArrived where someNewEvent is outside the class file, actually in the form.cs:
// code in the form
HIDNewDeviceEventMonitor ok = new HIDNewDeviceEventMonitor();
ok.Inserted += someNewEvent; // <-- my problem, I don't know how to add an event to the class this way
private void someNewEvent()
{
//Enumerate and add to listbox1
}
private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
ok.Dispose();
}
I 've seen this thing with other classes, how can I make my class like that?
Your Inserted event should look like this:
public event EventHandler Inserted;
You invoke it like this:
private void OnInserted()
{
if (this.Inserted != null)
{
this.Inserted(this, EventArgs.Empty);
}
}
The signature for the event handler is this:
void someNewEvent(object sender, EventArgs e)
{
//
}
Then you should wrap that code in the constructor of the class:
HIDNewDeviceEventMonitor ok;
public ClassName()
{
ok = new HIDNewDeviceEventMonitor();
ok.Inserted += someNewEvent; // <-- my problem
}
Declare the ok variable outside the constructor, and instantiate it inside. Then add the event handler.
Pro tip: You could use the generic EventHandler<T> if you need to supply a custom implementation of e.
Simply put, you're trying to add events to your HIDNewDeviceMonitor class.
To do this, first you'll need to define a delegate.
public delegate void InsertedHandler;
Next, you'll need to define the event in your HIDNewDeviceMonitor class.
// Notice how the event uses the delegate that's been defined
// v
public event InsertedHandler Inserted;
Now you'll need something that "fires" the event, which could easily be put in your watcher_EventArrived method.
void watcher_EventArrived(object sender, EventArrivedEventArgs e)
{
Debug.WriteLine("my device is inserted..");
// Notice how we check the event handler for null.
// If you don't, it could throw a NullReferenceException.
// Irritating, but easy to debug.. Usually..
if (Inserted != null)
Inserted(); // Or whatever parameters you need.
}
We're all done with the HIDNewDeviceMonitor class.
Now whatever class that uses the HIDNewDeviceMonitor can use the EventHandler code that you provided.
However, it'll have to be the same delegate.
public class MyClass
{
HIDNewDeviceMonitor monitor;
public MyClass()
{
monitor = new HIDNewDeviceMonitor();
monitor.Inserted += DeviceInserted;
}
private void DeviceInserted()
{
// Execute code here
}
}
You need to do following in the HIDNewDeviceEventMonitor class:
1.) First define a public event inside the class like this-
public event EventHandler Inserted;
2.) Then fire this event within the code where you detect the changes in events. Like this-
if(Inserted != null)
Inserted(this,null);
The if condition checks if the event is registered by any listener. It's fired in case it is.
Hope this helps.