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Raise control event programmatically in Xamarin.Forms

I have a button defined in XAML:
<Button x:Name="loginButton" Text="Login" Clicked="OnLoginButtonClicked" />
Is there a possibility to raise the Clicked event programmatically? Of course I could call OnLoginButtonClicked, but I'm interested how the Clicked event itself can be raised.

If you just want to call the Clicked action, you can do this trick:
var b = new Button();
b.Clicked += (x, y) =>
{
//Your method here
};
var t = b as IButtonController;
t.SendClicked(); //This will call the action
It is important to note this is not the right one.
As it was mentioned before, calling the actual method is preferred.

You can call DoSomething by event handler or any other place in your code
void OnLoginButtonClicked(object sender, EventArgs e)
{
DoSomething ();
}
private void DoSomething()
{
//Click code here.
}

Assing a delegate method
testButton3.TouchUpInside += HandleTouchUpInside;
Add the method
void HandleTouchUpInside (object sender, EventArgs ea)
{
new UIAlertView("Touch3", "TouchUpInside handled", null, "OK", null).Show();
}

pass method to event handler in C# WPF

This works in adding an event handler in C# WPF
CheckBox ifPrint = new CheckBox();
ifPrint.AddHandler(CheckBox.ClickEvent, new RoutedEventHandler(
(sender, e) => //toggle check box event
{
//do stuff
}));
but it looks messy when the method body gets long, so I want to define the method elsewhere like this
ifPrint.AddHandler(CheckBox.ClickEvent, delegate(object sender, RoutedEventArgs e){
checkBoxClick(sender, e);
});
private void checkBoxClick(object sender, RoutedEventArgs e)
{
//do stuff
}
but this doesn't even compile with the error: Cannot convert anonymous type to type 'System.Delegate' because it is not a delegate type
Sorry, I am new to this and have no idea how it's supposed to be done. Is this even close? Thanks!

You can subscribe to a separate method like this, as long as the signature of checkBoxClick is correct:
ifPrint.Click += checkBoxClick;
You can also subscribe to an event inline like this:
ifPrint.Click += (s, e) => SomeMethod();
Which then allows you to name your method something more reasonable and not require it to accept parameters:
private void SomeMethod()
{
//do stuff
}
Just to explain it a little further, in the above code, s and e take the place of the parameters in your checkBoxClick event method, so it's basically equivalent to this:
ifPrint.Click += checkBoxClick;
private void checkBoxClick(object sender, RoutedEventArgs e)
{
SomeMethod();
}
Edit, in regards to your comment.
Given this is much simpler, when, if ever, should one use this? ifPrint.AddHandler(CheckBox.ClickEvent, new RoutedEventHandler( (sender, e) => { //do stuff }));
I honestly don't think I've ever used that syntax.
It seems that in most cases it does the same thing. According to the MSDN docs, there's a handledEventsToo parameter on the AddHandler() method, which I think could be significant.
Imagine you subscribed to an event multiple times, like this:
ifPrint.Click += checkBoxClick;
ifPrint.Click += checkBoxClick;
ifPrint.Click += checkBoxClick;
And inside your event, you set e.Handled = true. If you didn't have that line, you'd see the message box displayed 3 times. But with that line, you only get the message box once, because the first time the event fires, it marks the event "handled".
private void checkBoxClick(object sender, RoutedEventArgs e)
{
MessageBox.Show("Clicked!");
e.Handled = true;
}
By passing in true for the last parameter (it's false by default), you actually tell it to fire that event, even if other events already "handled" the event.
ifPrint.AddHandler(CheckBox.ClickEvent,
new RoutedEventHandler((s, e) => { /* do stuff */ }), true);

try this logic to attach click event handler for your checkbox.
CheckBox ifPrint = new CheckBox();
ifPrint.Click+=checkBoxClick;
private void checkBoxClick(object sender, RoutedEventArgs e)
{
//do stuff
}

How to invoke event handler mentod added to control? [duplicate]

This question already has an answer here:
Closed 10 years ago.
Possible Duplicate:
How can I invoke an event handler from a function?
I need to do something I was pretty sure should be simple, I have Form with controls and every control have event handler that sets label with correct formating etc.
What I need is to call every handlers collection for every control on specific type.
I browsed all stackoverflow and never saw result.
It is simple application so please stop comments like: "you need additional function called from event handler".
This is what I tried
foreach (Control ctrl in Controls)
{
if (ctrl is TrackBar)
{
TrackBar tb = ctrl as TrackBar;
Invoke(tb.Scroll, tb, new EventArgs());
}
}
But I see very strange error
The event 'System.Windows.Forms.TrackBar.Scroll' can only appear on the left hand side of += or -=
Any solution?

You can't raise event outside class in which event is declared (only adding and removing handlers is available). Instead of trying to raise event, which will call event handler, simply extract handler logic to separate method, and call that method:
foreach (TrackBar tb in Controls.OfType<TrackBar>())
{
DoSomething(tb.Value);
}
And handler:
void trackBar_Scroll(object sender, EventArgs e)
{
DoSomething(((TrackBar)sender).Value);
}

Error appears because tb.Scroll is event not delegate.

You could try making a delegate with the same Signature as the Event, create a common eventhandler for your controls and then you can either invoke it or respond to the event as normal.
i.e.
Something like this:
public partial class Form1 : Form
{
public delegate void trackbarscroll( object sender, EventArgs e);
trackbarscroll tbs;
public Form1()
{
InitializeComponent();
trackBar1.Scroll += new EventHandler(trackBar_Scroll);
trackBar2.Scroll += new EventHandler(trackBar_Scroll);
tbs = trackBar_Scroll;
}
void trackBar_Scroll(object sender, EventArgs e)
{
TrackBar tb = (TrackBar)sender;
}
private void button1_Click(object sender, EventArgs e)
{
foreach (Control ctrl in Controls)
{
if (ctrl is TrackBar)
{
TrackBar tb = ctrl as TrackBar;
Invoke(tbs,tb, new EventArgs());
}
}
}
}

Event fires more and more times

I have a silverlight mvvm application that loads main view with 2 user controls loaded into 2 ContentControls, one with listbox showing items and other with edit button. When i click edit button, 2 new user controls load into the ContentControls, one showing data to edit (EditData) and other having Save and Cancel button (EditAction).
When i click save button, it raises an event that is defined in seperate GlobalEvents.cs class like:
public event EventHandler OnSaveButtonClicked;
public void RaiseSaveButtonClicked()
{
this.OnSaveButtonClicked(this, EventArgs.Empty);
}
and i subscribe to it in the other user control EditData, because i need to transfer that edited data via custom EventArgs, so i have put in the constructor of it's ViewModel:
this.globalEvents.OnSaveButtonClicked += (s, e) => SaveData();
and in the Save data:
public void SaveData()
{
globalEvents.RaiseSaveData(EditedGuy);
}
which raises another event that loads previous user controls into their ControlContent and shows edited data in list box. Thats all fine, but whenever i click on edit and then save again, it raises the event twice, and again 3 times, then 4 and so on. How can i make it to be raised only ONE time? I thought it could be because every time i click edit, a new instance of the user control is loaded and i dont know, maybe the subscription to the event stays, so i have tried to paste
this.globalEvents.OnSaveButtonClicked -= (s, e) => SaveData();
to the Dispose() method but without success. How can i make this work?

You can't use lambdas when you want to unregister from events.
this.globalEvents.OnSaveButtonClicked += (s, e) => SaveData();
This will create one instance - let's call it instance A - of type EventHandler and add it as a handler.
this.globalEvents.OnSaveButtonClicked -= (s, e) => SaveData();
This will not remove instance A from the event but create a new instance - instance B - and tries to remove it from the event.
To fix this problem, either create a little method or save that anonymous method in a field:
class ViewModel
{
private EventHandler _saveButtonClickedHandler;
// ...
public ViewModel()
{
_saveButtonClickedHandler = (s, e) => SaveData();
this.globalEvents.OnSaveButtonClicked += _saveButtonClickedHandler;
// ...
}
public void Dispose()
{
this.globalEvents.OnSaveButtonClicked -= _saveButtonClickedHandler;
// ...
}
// ...
}

this.globalEvents.OnSaveButtonClicked += (s, e) => SaveData();
This line is being called multiple times so you are adding a new event handler every time.
You need to either move that line to somewhere where it's only called once or change the event handler to:
this.globalEvents.OnSaveButtonClicked += SaveData;
public void SaveData(object sender, EventArgs e)
{
globalEvents.RaiseSaveData(EditedGuy);
this.globalEvents.OnSaveButtonClicked -= SaveData();
}
So you remove the event handler after dealing with it. This assumes that the handler will be added back next time you go into edit mode.

You could define a private eventhandler delegate variable in your class and assign it in your constructor:
private SaveButtonClickedHandler _handler;
Assign the handler in your constructor:
_handler = (s,e) => SaveData();
this.globalEvents.OnSaveButtonClicked += _handler;
Dispose:
this.globalEvents.OnSaveButtonClicked -= _handler;
"SaveButtonClickedHandler" is pseudo-code/placeholder for whatever the name of the delegate should be.
Hasanain

You'll have to put in a proper event handler method that calls SaveData() and register/unregister that. Otherwise you try to unregister another "new" anonymous method instead of the original one you've registered, which you, because it is anonymous, cannot actually access anymore.
public void SaveButtonClicked(object sender, EventArgs e)
{
SaveData();
}
this.globalEvents.OnSaveButtonClicked += SaveButtonClicked;
this.globalEvents.OnSaveButtonClicked -= SaveButtonClicked;

Custom Component On Click Event

I've built a custom component that basically has a picture box and label in it. In the parent form, I want to be able to detect when its been clicked on. The standard .click event doesn't seem to be working, but I've never used events before so am unsure if I'm using them correctly. Heres the code I'm using (in the parent) to try and make it recognise the click:
Item aItem = new Item();
aItem.Icon = ItemImage;
aItem.Title = Title;
aItem.Click += new EventHandler(ItemClicked);
aItem.Filename = File;
and heres the method its calling:
public void ItemClicked(Object sender, EventArgs e)
{
MessageBox.Show("Item Clicked!");
}
This code never fires. Do I need to put anything into the component or am I just doing this wrong?
Cheers

Right I finally worked it out. Tejs response just confused me more so here's what I did.
In my UserControl I had the following event:
public event EventHandler Clicked;
Then I had an event for when the image was clicked (still in the UserControl) and I just called the Clicked event:
private void imgItem_Click(object sender, EventArgs e)
{
Clicked(this, e);
}
Then in my parent form, when I created the object, I had the following:
Item aItem = new Item();
aItem.Clicked += new EventHandler(ItemClicked);
void ItemClicked(object sender, EventArgs e)
{
MessageBox.Show("Clicked!");
}

You would do this by exposing an event':
Your custom component:
// A custom delegate like MyItemClickedHandler, or you could make a Func<> or Action<>
public event MyItemClickedHandler ItemClickedEvent;
public void ItemClicked(object sender, EventArgs e)
{
if(ItemClickedEvent != null)
ItemClickedEvent(); // Your delegate could pass parameters if needed
}
Then your parent form simply observes the event:
myCustomControl.ItemClickedEvent += new MyItemClickedHandler(SomeMethod);
Then, whenever the event is raised on your custom control, the parent is notified because it subscribed the event.