Actually, I want to know how to add it's click event.
Button b = new Button();
b.Text = "Go back!";
b.ID = "btn_Back";
b.Click = ??
b.Click += new EventHandler(btn_Click);
and then declare btn_Click, like:
void btn_Click(object sender, EventArgs e)
{
throw new NotImplementedException();
}
If you're in VS2005 versions, once you hit b.Click += you'll be queried to hit TAB and declare it all automatically!
Kind regards,
Henrik.
Here is how to register the event handler (using the += notation):
b.Click += new EventHandler(NameOfHandler);
You will need a function called NameOfHandler that corresponds to the EventHandler delegate - that is, that takes a first parameter of type object and a second paremeter of type EventArgs:
public void NameOfHandler(object o, EventArgs e)
{
// code here
}
Normally, in visual studio once you have typed the += following the event name, tabbing a couple of times will generate the rest of the line and an empty event handler function.
Button b = new Button();
b.Text = "Go back!";
b.ID = "btn_Back";
b.Click += new EventHandler(B_Click);
Controls.Add(b);
// ...
private void B_Click(object sender, EventArgs e)
{
// ...
}
Related
I'm creating Buttons programmatically with a method and am wanting to attach a Click event handler. However, that data currently comes from a string parameter which can't be used with += RoutedEventHandler.
public Button CreateButton(string Display, string Name, string ClickEventHandler)
{
Button Btn = new Button
{
Content = Display,
Name = "Btn_" + Name
};
Btn.Click += new RoutedEventHandler(ClickEventHandler);
return Btn;
}
void Btn_save_Click(object sender, RoutedEventArgs e)
{
throw new NotImplementedException();
}
// later
Button MyButton = CreateButton("Save", "save", "Btn_save_Click");
Error is RoutedEventHandler expects a Method and not a String. Is there a different approach to programmatically binding events that allows this sort of behaviour?
Thanks
From what I understand you wish to pass the method that should be executed when Click event is triggered. You could do something along the lines of:
Button button = CreateButton("Save", "save", (s, e) => SomeOnClickEvent(s, e));
Button button2 = CreateButton("Create", "create", (s, e) => SomeOtherOnClickEvent(s, e));
public Button CreateButton(string display, string name, Action<object, EventArgs> click)
{
Button b = new Button()
{
Content = display,
Name = $"Btn_{name}"
};
b.Click += new EventHandler(click);
return b;
}
void SomeOnClickEvent(object sender, EventArgs e)
{
}
void SomeOtherOnClickEvent(object sender, EventArgs e)
{
}
I am not entirely sure what you are trying to accomplish with this.
Here is an example of how to create an event at run time.
public void CreateButton()
{
Button Btn = new Button();
Btn.Click += new EventHandler(btn_Clicked);
}
private void btn_Clicked(object sender, EventArgs e)
{
// Your Logic here
}
I’m trying to dynamically declare an ImageButton.
I declare it and assign an ID and Image to it as follows:
ImageButton btn = new ImageButton();
btn.ImageUrl = "img/Delete.png";
btn.ID = oa1[i] + "_" + i;
btn.OnClick = "someMethod";
But when I try to assign an OnClick handler for the button it throws the following exception:
System.Web.UI.WebControls.ImageButton.OnClick is inaccessible due to protection level
You couldn't assign a value to a method like that, even if it were accessible. You need to subscribe to the event:
btn.Click += ClickHandlingMethod;
Take a look at this answer, it is related with dynamic controls and events
As Jon commented you cannot add a string to the event, in this case you need to add a handler for the event:
protected void Page_Init(object sender, EventArgs e)
{
var i = new ImageButton();
i.Click += new ImageClickEventHandler(i_Click);
this.myPanel.Controls.Add(i);
}
void i_Click(object sender, ImageClickEventArgs e)
{
// do something
}
Alternativeley
protected void Page_Init(object sender, EventArgs e)
{
var i = new ImageButton();
i.Click += (source, args) =>
{
// do something
};
this.myPanel.Controls.Add(i);
}
An example:
private void CreateAButton()
{
var button = new ImageButton();
button.ImageUrl = "yourimage.png";
button.ID = "Button1";
button.Click += ButtonClick;
Page.Form.Controls.Add(button);
}
private void ButtonClick(object sender, ImageClickEventArgs e)
{
// Do stuff here
// ...
}
You can use this code (one significant change) :
private void CreateAButton()
{
var button = new ImageButton();
button.ImageUrl = "yourimage.png";
button.ID = "Button1";
button.PostBackUrl = "http://www.towi.lt";
Page.Form.Controls.Add(button);
}
Trick is in "PostBackUrl". If you write correct link it will redirects to it (as in example). In other cases this will add original server name, '/' and text you entered. For example 'xxx' will be turned to "http://yourservername/xxx". It is very useful, when you working with redirects to same ISS, but different sites and dynamically creating buttons for users.
I came to the same question again and again. I need to use the user entered values after a button event, or a doubleclick, or anything. when I do it with the designer, it passes automatically the txt control and its value to the whole program, and I can use it anywhere. But programatically I couldn't solve it.
here's a little example:
private void Form1_Load(object sender, EventArgs e)
{
string blabla = "anything";
Button btn = new Button();
btn.Location = new Point(10, 40);
btn.Text = "Click me";
btn.Click += new EventHandler(btn_Click);
this.Controls.Add(btn);
}
void btn_Click(object sender, EventArgs e)
{
MessageBox.Show(blabla);
}
this doesn't work, so I added a "public" and the script goes:
public string blabla;
private void Form1_Load(object sender, EventArgs e)
{
blabla = "anything";
Button btn = new Button();
btn.Location = new Point(10, 40);
btn.Text = "Click me";
btn.Click += new EventHandler(btn_Click);
this.Controls.Add(btn);
}
void btn_Click(object sender, EventArgs e)
{
MessageBox.Show(blabla);
}
And so I can use my variable with the changed values. This goes well with controls too.
This works, but this makes thousands of public variables in a bigger application. How can I increase the readability by losing these publics? Is there a way to use "ref"? I saw it on the automatic "extract method", I just don't know, how can I use that with events.
Maybe I am on the wrong track in this, if there is a shortcut or other solution, please help.
The important change between the two snippets wasn't the fact that you made the variable public - it's that you changed it from a local variable in the Form1_Load method into an instance variable. It can still be a private instance variable, if you're handling it in the same class.
However, another alternative is to keep it as a local variable but use an anonymous function to handle the event:
private void Form1_Load(object sender, EventArgs e)
{
string blabla = "anything";
Button btn = new Button();
btn.Location = new Point(10, 40);
btn.Text = "Click me";
btn.Click += (sender, args) => {
MessageBox.Show(blabla);
// Other code here, but hopefully not too much...
};
this.Controls.Add(btn);
}
(As noted, you don't want to make the anonymous function too big, for the sake of readability - but it can always call another method with all the appropriate state.)
EDIT: As you're using VS2005, you're only using C# 2 so you can't use lambda expressions. You can use anonymous methods though. The code would then be:
private void Form1_Load(object sender, EventArgs e)
{
string blabla = "anything";
Button btn = new Button();
btn.Location = new Point(10, 40);
btn.Text = "Click me";
btn.Click += delegate {
MessageBox.Show(blabla);
// Other code here, but hopefully not too much...
};
this.Controls.Add(btn);
}
All winforms controls tend to have a Tag property, of type object which you can use to store your own custom data if you wish. Its not particularly good practice, and shows up some other architectural problems but here you go:
private void Form1_Load(object sender, EventArgs e)
{
Button btn = new Button();
btn.Location = new Point(10, 40);
btn.Text = "Click me";
btn.Click += new EventHandler(btn_Click);
btn.Tag = "blahblah";
this.Controls.Add(btn);
}
void btn_Click(object sender, EventArgs e)
{
Button btn = (Button)sender;
MessageBox.Show(btn.Tag.ToString());
}
You can do it with lambdas.
btn.Click += (sender, e) => { MessageBox.Show(blabla); }
You can do it my making a closure inside the Form1_Load method like this
private void Form1_Load(object sender, EventArgs e)
{
blabla = "anything";
Button btn = new Button();
btn.Location = new Point(10, 40);
btn.Text = "Click me";
btn.Click += (s,e) => MessageBox.Show(blabla);
this.Controls.Add(btn);
}
Even if blabla goes out of scope, the closure will still know that it contained the text "anything" when you click the button.
I add buttons dynamically.. e.g. Button newButton=new Button();
Now i want each button to be triggered. So i wrote them the following events:
public void response_Click(object sender, EventArgs e)
{
}
public void edit_Click(object sender, EventArgs e)
{
}
public void quote_Click(object sender, EventArgs e)
{
}
Button quote = new Button();
Button reply = new Button();
Button edit = new Button();
quote.ID = "quote";
reply.ID = "reply";
edit.ID = "edit";
How do i trigger them, as soon as the user clicks on the button..will my functions above be triggered? do i need to do the following:
this.Clicked+=quote;
this.Clicked+=reply;
this.Clicked+=edit;
if i do need to do that..where do i put those lines of code?
i use visual studio 1010. asp.net
You can do like..
quote.Click += new EventHandler(quote_Click);
reply.Click += new EventHandler(response_Click);
edit.Click += new EventHandler(edit_Click);
Yes, you would need to register the event of the button and associate it with particular method.
for example.
myButton.Click += new EventHandler(Button_Click);
void Button_Click(object sender, EventArgs e)
{
}
I am creating one button on a page dynamically. Now I want to use the button click event on that button.
How can I do this in C# ASP.NET?
Button button = new Button();
button.Click += (s,e) => { your code; };
//button.Click += new EventHandler(button_Click);
container.Controls.Add(button);
//protected void button_Click (object sender, EventArgs e) { }
The easier one for newbies:
Button button = new Button();
button.Click += new EventHandler(button_Click);
protected void button_Click (object sender, EventArgs e)
{
Button button = sender as Button;
// identify which button was clicked and perform necessary actions
}
Simply add the eventhandler to the button when creating it.
button.Click += new EventHandler(this.button_Click);
void button_Click(object sender, System.EventArgs e)
{
//your stuff...
}
It is much easier to do:
Button button = new Button();
button.Click += delegate
{
// Your code
};
You can create button in a simple way, such as:
Button button = new Button();
button.Click += new EventHandler(button_Click);
protected void button_Click (object sender, EventArgs e)
{
Button button = sender as Button;
// identify which button was clicked and perform necessary actions
}
But event probably will not fire, because the element/elements must be recreated at every postback or you will lose the event handler.
I tried this solution that verify that ViewState is already Generated and recreate elements at every postback,
for example, imagine you create your button on an event click:
protected void Button_Click(object sender, EventArgs e)
{
if (Convert.ToString(ViewState["Generated"]) != "true")
{
CreateDynamicElements();
}
}
on postback, for example on page load, you should do this:
protected void Page_Load(object sender, EventArgs e)
{
if (Convert.ToString(ViewState["Generated"]) == "true") {
CreateDynamicElements();
}
}
In CreateDynamicElements() you can put all the elements you need, such as your button.
This worked very well for me.
public void CreateDynamicElements(){
Button button = new Button();
button.Click += new EventHandler(button_Click);
}
Let's say you have 25 objects and want one process to handle any one objects click event. You could write 25 delegates or use a loop to handle the click event.
public form1()
{
foreach (Panel pl in Container.Components)
{
pl.Click += Panel_Click;
}
}
private void Panel_Click(object sender, EventArgs e)
{
// Process the panel clicks here
int index = Panels.FindIndex(a => a == sender);
...
}