I am generating a number of buttons with similar or identical content and was hoping to use the names they are given to differentiate them. As the program is creating the buttons dynamically I can't create a separate event for them all and instead need to be able to grab the name to be able to know which button triggered the event.
Is there a way to pass through the name of a button to the click event it initiates? the sender object seems to contain the content but not the name.
It is for a event like this:
private void Button_Click(object sender, RoutedEventArgs e)
{
//getname of button
Canvas.Children.Remove(//name of button\\)
}
Far as I know, WPF does not even assign anything to the Name property automatically - that's just for developers to assign so we can reference the control.
However, you should be able to just pass in the sender to the remove method since it accepts a UIElement argument which Button is derived from.
Canvas.Children.Remove((Button)sender);
I'm not familiar with WPF. If this answer appears to be a junk, I'll delete it.
In ASP.Net, we can cast to a button to get the sender's information. Something like this -
private void Button_Click(object sender, RoutedEventArgs e)
{
var button = sender as Button;
button.Name
}
Perhaps getting at the control's name will work for you
private void button1_Click(object sender, RoutedEventArgs e)
{
Control control = (Control)sender;
Canvas.Children.Remove(control.Name);
}
Related
When I manually cast the object sender and Eventargs e to a class like below what is it I am exactly doing? I know that it allows me to access all the arguments that have been passed and also to manipulate the object sender (as below):
private void Button1_Click(object sender, EventArgs e)
{
/ /casting the arguments
MouseEventArgs eventargs = e as MouseEventArgs;
Button button1 = sender as Button;
// displays which mouse button I used
MessageBox.Show(eventargs.Button.ToString());
// displays the name of the button I clicked
MessageBox.Show(button1.Name.ToString());
// changes the text of the button
button1.Text = "Ive changed";
}
I feel like I don't understand how this works, only that it works.
Also, it seems quite easy to write an event handler that serves several objects of the same type, but not one that can handle different types of event or different types of object ie:
private void Generic_Event_Handler(object sender, EventArgs e)
{
// displays what object and event triggered the handler
MessageBox.Show(sender.ToString());
MessageBox.Show(e.ToString());
}
Is this ever used? Is there a decent explanation of eventhandlers out there?
The following signature
private or protected void EventHandlersName (object sender, EventArgs e)
is the signature that they have all the event handlers in .NET. The parameter called sender is associated with the object on which the event called e was raised.
Why the type of sender is object?
Because all types in .NET has as their base type the type System.Object. So this way it doesn't make any difference if we have a click event on button on a win form, or in a WPF applciation or in an ASP.NET web form button.
Why we should manually cast the object sender?
We should do so, in order we have access to the properties and the methods of the specific type we have in each case.
For instance, all controls may not have a property called Name. Furthermore the base type called System.Object doesn't have. So if you don't cast the object sender to a Button class, then you can't read it's property called Name.
The signature of an event handler in .Net is (or at least should be):
(object sender, XXArgs e) where XXArgs is a class that inherits from EventArgs.
sender is, well, the sender of the event. In your example, if you click on a button, the button will fire the event using its own instance reference (this) for the sender parameter (so sender is a reference to your button). This is useful because you don't need to store references to the sender of the event ; it's available right here in the event handler.
For the XXArgs part, it contains information about the event. You shouldn't cast it actually, but write your handler with the right signature.
Basically, for a mouse click on a button, the right signature of the event handler would be:
private void Control_MouseClick(Object sender, MouseEventArgs e)
{
}
sender is a reference to type object. The actual object that it refers to could be anything; (in the specific case of an event handler, if everything is working as intended it should refer to the control that generated the event). When you say:
Button button1 = sender as Button;
you are trying to use a Button reference to refer to the same underlying object. If the underlying object is compatible (ie: is a Button), then the button1 reference will enable you to utilize the Button members of the underlying object. Otherwise, with the sender reference, you would only have been able to utilize the object members of the underlying object.
Note that it could still be something more "concrete" or specific than a Button, and then you would need a different cast to get at the more derived members.
Also you can cast page in case of protected void Page_Load(object sender, EventArgs e)
var senderInfo = (Page)sender;
I'm having a ContextMenu, and I need to determine what control has it been opened on in the event ContextMenu_Opening.
The event arguments do not contain such information, or either the sender. How can I do that?
Solved by using a simple property which I had no idea it existed..:
private void contextMenu1_Opening(object sender, CancelEventArgs e)
{
MessageBox.Show(contextMenu1.SourceControl.Name);
}
Day 1 coder here:
private void button1_Click(object sender, EventArgs e)
{
}
private void Form1_Load(object sender, EventArgs e)
{
string firstName;
}
In Visual C# Express, I changed my button name (through properties) from button1 to btnString, but as you can see it is not adapting in the code.
Did I do something wrong ?
private void button1_Click(object sender, EventArgs e)
{
}
This is the event handler, and by changing the control's name it won't automatically change the event handler name (because it was created prior to changing the control's name), you can manually do it though. You can also change it through the properties window, change the tab to "events" instead of the default selected "properties" tab
Changing the button name seemingly hasn't updated the Click event handler.
Either go to the button properties event tab, and update the button1_Click to btnString_Click and the same to the event function, or delete the button1_Click function and double click the button again, so visual studio will generate the correct handler name.
When you change the name of a control, the designer will search your code and replace instances where you have used that variable name, but it will not change the name of event handlers.
Why? What if instead of the "default name" (for a button click it would be <buttonName>_Click) you had your own custom name, like MyCoolEventHandler_Click? The designer would not know how to rename that. The same thing applies if you have coincidentally used a variable name in a totally unrelated function. Would you want it changing the name on you?
You have to do these changes manually. My best advice is to name the controls before you create event handlers. But you can always go into the Properties panel and change the links.
private void textBox1_MouseClick(object sender, MouseEventArgs e)
{
textBox1.SelectAll();
}
This works but I have 6 textBoxes. Is there any easier way instead of adding event listeners for each and every textbox? Or a shorthand or something?
Thanks.
Add the same event handler to each and have ((TextBox)sender).SelectAll() to ensure the one that is clicked on is highlighted.
If you're looking for something more generic create a derived class of TextBox containing the same.
In Visual C# Form Application, When I Click on the button I want to add to the other controls(like listboxes,labels,textboxes) in same form.
How do I do this?
I have no idea what "to come to the other controls" might mean. But the event handlers in your Form derived class is the switchboard. Implement the button's Click event and have it do whatever you want done with any other controls. A trivial example:
private void button1_Click(object sender, EventArgs e) {
label1.Text = "You clicked the button!";
}
In the form designer, add an event handler to the button's Click event.
The form designer will give you a new method like this; add your code into this method:
private void button_Click(object sender, EventArgs e)
{
// Write some code that uses list boxes, labels, text boxes etc.
}
You question is somewhat unclear, but if you simply want to access other controls on the form, just go ahead and do so:
private void YourButton_Click(object sender, EventArgs e)
{
string someValue = yourTextBox.Text;
// do something with the value
}
If you want to add one event handler to many controls, you can do it.
Just go to properties of control you wish to subscribe, find appropriate event from list (ex: onClick) and choise your existed handler.
But this method will be sutable if events compotable.
Describe your task more detail.