Through Visual Studio you can easily create a method for an event (button click, etc). Is there a way to create a method for multiple events, like a method that would run any time one of three buttons were clicked, or one of many textboxes were typed in?
Once you've created the method once you should be able to use it for any other event that has a similar signature.
From the Designer, don't double-click the method but instead drop down the list for any existing event handler that can be assigned to your chosen event.
Like #lcfseth notes, you can identify which particular control sent the message via the object sender argument.
Yes ,you can bind many events to the same method (events of the same signature)
firstEvent += MyMethod;
secondEvent += MyMethod
You can assign the same handler to Click events of multiple controls. sender points to the control that caused the event.
When you bind a function to an object's event you're actually passing a delegate (i.e. a pointer-to-function) to its event handler. You can bind the same function to as many objects' event handlers as you want, as long as the required delegate's signature corresponds.
Button1.Click += new EventHandler(this.AnyButton_Click);
Button2.Click += new EventHandler(this.AnyButton_Click);
Button3.Click += new EventHandler(this.AnyButton_Click);
In case you need to run specific operations on the "sender" object depending on which button was clicked pay attention that the function's argument "sender" is the button you clicked so if you need to work on the button object remember to unbox it to its specific class (i.e. cast it to Button or whatever its type is).
void AnyButton_Click(Object sender, EventArgs e)
{
Button clickedButton = (Button)sender; // unbox the sender
MessageBox.Show("You just clicked button " clickedButton.Text);
}
(MSDN)
Related
What do sender and eventArgs mean/refer to? How can I make use of them (for the scenario below)?
Scenario:
I'm trying to build a custom control with a delete function, and I want to be able to delete the control that was clicked on a page that contains many of the same custom control.
The sender is the control that the action is for (say OnClick, it's the button).
The EventArgs are arguments that the implementor of this event may find useful. With OnClick it contains nothing good, but in some events, like say in a GridView 'SelectedIndexChanged', it will contain the new index, or some other useful data.
What Chris is saying is you can do this:
protected void someButton_Click (object sender, EventArgs ea)
{
Button someButton = sender as Button;
if(someButton != null)
{
someButton.Text = "I was clicked!";
}
}
sender refers to the object that invoked the event that fired the event handler. This is useful if you have many objects using the same event handler.
EventArgs is something of a dummy base class. In and of itself it's more or less useless, but if you derive from it, you can add whatever data you need to pass to your event handlers.
When you implement your own events, use an EventHandler or EventHandler<T> as their type. This guarantees that you'll have exactly these two parameters for all your events (which is a good thing).
Manually cast the sender to the type of your custom control, and then use it to delete or disable etc. Eg, something like this:
private void myCustomControl_Click(object sender, EventArgs e)
{
((MyCustomControl)sender).DoWhatever();
}
The 'sender' is just the object that was actioned (eg clicked).
The event args is subclassed for more complex controls, eg a treeview, so that you can know more details about the event, eg exactly where they clicked.
'sender' is called object which has some action perform on some
control
'event' its having some information about control which has
some behavoiur and identity perform
by some user.when action will
generate by occuring for event add
it keep within array is called event
agrs
FYI, sender and e are not specific to ASP.NET or to C#. See Events (C# Programming Guide) and Events in Visual Basic.
Say I added a series buttons to a WPF app progammatically, as part of a label, textbox, button section, and attached a single handler to the click event of all of these. How can I specify which button (pertaining to which section) is being clicked, so it can be handled accordingly?
Attaching individuals handlers won't work since the user must be able to add as many of these 'lines' as needed.
A possible alternative would be to pass information to the event handler, such as:
...
var sender = this;
var args = new CustomEventArgs(sectionName);
var button = new Button();
button.Click += Button_EventHandler_Click(sender, args);
But I haven't found a way to this in C#.
Any help/idea will be appreciated!
Thanks
Look at the sender parameter, it will be the clicked button.
If you need to further differenciate the buttons, you can set the Tag property of the button.
My UserControl contains various controls. I made an event handler for its click event. I want the event handler to fire / be called when the user clicks anywhere on my user control.
This is the method I use to add my UserControl to my WinForms application.
private void addContact(some parameters here)
{
//This is my usercontrol
contactsListItem.contactsListItem contact = new contactsListItem.contactsListItem();
//
//some codes here
//
//Adding an event handler for the click event
contact.Click += new EventHandler(contact_Click);
//Adding the UserControl to my application
flowLayoutPanel_contactsList.Controls.Add(contact);
}
The contact_Click(...) event handler should change the background of my UserControl. I have tried stepping into the code to see if the event handler fires and I found out that it doesn't fire no matter where I click on my UserControl.
I have searched through the internet. I encountered terms like delegate, subscribers and publishers.
What should I do to make the event handler for my UserControl's click event to fire?
What is the structure of your user control? Click events are not bubbled in WindForms, hence if you are clicking on a control WITHIN your user control, the latter won't fire any Click event.
EDIT:
The simplest solution is to manually bubble the event from each child by attaching a handler in your user control:
child1.Click += new EventHandler(child_Click);
child2.Click += new EventHandler(child_Click);
child3.Click += new EventHandler(child_Click);
and inside child_Click fire off your Click event:
this.OnClick(e);
You seem to be on the right track however it is not clear what your contact here is. Typically you use delegates (essentially pointers to functions) for methods that have arguments to be passed:
if (bDeleteRdClick)
DeleteRD.Click -= delegate { DeleteRDClick(this.Object); };
DeleteRD.Click += delegate { DeleteRDClick(this.Object); };
where you are sure to remove pre-existing delegates, otherwise they will 'stack-up', firing multiple methods when not required.
For the method above, using an EventHandler seems to me to be the right approach, but as I state above, a check on whether contact is of the correct type would not go unmissed:
if (this.contact.GetType() == typeof(RibbonButton))
{
RibbonButton Rb = (RibbonButton)contact;
Rb.Click += new EventHandler(contact_Click);
}
I hope this is of some help.
I have some code that creates panels with picture boxes in them. I would like something to tell me what picture box was clicked on.
I'm using the following:
PicBx[z].Click += new EventHandler(clicked);
Do I need to assign a value on the click? Or is there a way just to display what you clicked on?
The handler method gets the control that was clicked as its sender parameter.
You can cast it to PictureBox and do whatever you want with it.
Alternatively, you can add an anonymous method as the handler:
PicBx[z].Click += delegate { SomeMethod(z, somethingElse); };
However, make sure not to close over the loop variable.
The clicked method does have an argument passed into it (Object sender). This is the PictureBox that was clicked.
Your event handler will have two arguments in its signature: object sender and EventArgs e. The sender is the object that you clicked on, so you can cast it to PictureBox or whatever type it actually is, and you should be good to go.
I have a lot of buttons in my project. To make the program I shorter need to get every click of a button to the same "Button_click" method. Is this possible?
Thanks
Just use the same event handler for all the buttons. In code, this would be:
button1.Click += HandleButtonClick;
button2.Click += HandleButtonClick;
etc
It should be possible to do in the designer too.
If these are buttons in different forms, you'll need to either have a static handler method somewhere, or each form will need a reference to whatever class has the handler method. You may well need to add these handlers in code, rather than using the designer.
Yes - it's perfectly possible.
You don't say whether you're WinForms or WPF but the basic way is to create a private method that's the handler and then call that from each button handler:
private void ButtonHandler(some arguments)
{
}
private void OnButton1Click(object sender, EventArgs e)
{
ButtonHandler(some arguments);
}
However, you can just subscribe the same handler to each button's click event:
Button1.Click += ButtonHandler;
Button2.Click += ButtonHandler;
Or set these from the designer - just pick the existing method from the drop-down list rather than creating a new handler.
With WPF you can quite easily bind each button click to the same handler in XAML:
<Button x:Name="Button1" Click="ButtonHandler" ... />
<Button x:Name="Button2" Click="ButtonHandler" ... />
Again the designer gives you the choice of selecting an existing handler as well as creating a new one.
Yes, it's possible, just select the method you need in your Events tab of Properties Window designer (you can show it from the main menu: View -> Properties Window):
Or do it manually in <Formname>.Designer.cs file:
this.button1.Click += new System.EventHandler(this.button1_Click);
//...
this.button2.Click += new System.EventHandler(this.button1_Click);
Also, if you want to perform slightly different actions depenging of which button was pressed and still only use one method, use sender argument. Its value will always be a reference to the button that was clicked, so you can do some logic by looking at button's Name or Tag properties:
private void button1_Click(object sender, EventArgs e)
{
Button btn = (Button)sender;
switch((int)btn.Tag) {
case 1:
// action 1
break;
case 2:
// action 2
break;
}
}
Still, you should be careful with this and see if it really gives you any benefits to share an event handler instead of creating separate handlers for different buttons.