I have a problem that I can't resolve on the server side of my project.
I'll explain:
I have a page named Global,this is ASP.NET page.
This page uses a UserControl named CateGories.
Now I have a button on this UC page,that when I press I want to invoke a function on the Global page that makes a connection with my DB.
I decided to use delegates(events)
This is the code.
Global page:
//here i add my function to the event
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
ShowCurrentTime.Text = DateTime.Now.ToString();
}
CateGories ClassCat = new CateGories();
ClassCat.MainDel += PopulateLinks;
}
//this is the function that the event will run
public void PopulateLinks(string CategoryName)
{....}
Code of the UC page (CateGories):
//delegation of the event
public delegate void Click(string ButtonName);
public event Click MainDel = null;
//function that invokes when I click a button
protected void News_Click(object sender, EventArgs e)
{
if (MainDel != null)
{
MainDel(News.Text);
}
}
Now everythig should work fine, but there is a problem, when the compiler gets to the
if(MainDel!=null)
...
It doesn't get in the function, there go MainDel is null.
I can't see the problem here, why after I insert function to MainDel, its gets null eventualy...
I'll be happy if someone can help
thanks.
Max.
I think I've encountered this problem before, when working with web applications the way I would a windows application.
The problem lies in that when the page gets reloaded, a new instance of your page class is created so any values from the last server interaction are lost.
MainDel is indeed null for what I can see.
You're creating one instance of CateGories on your Web Form and another one on your User Control. And once you check it for beeing null on the UC the reference is to the not initialized object.
One possible way to do that is creating and adding the User Control programatically to the page before PageLoad() and keeping a reference to it so you can access it's properties.
Another solution could be using Page.FindControl to find the UC and make the subscription to the event.
The method names above may be incorrect, it's been a long time without working with web forms.
Related
On my form I have 2 UserControls (ButtonDiscount, ButtonAdvertisment) that inherit FadeControl. FadeControl inherits UserControl class and is used to do custom stuff on the controls like fade out.
My 2 UserControls each have just one button hence those two unimaginative names.
On click of that button on one of usercontrols, I need to access the method in FadeControl from the other UserControl. The other button does the opposite.
I've done the following, on the event click in the UserControl ButtonDiscount:
private void button1_Click(object sender, EventArgs e)
{
ButtonAdvertisment ba = (ButtonAdvertisment)this.Parent.Controls.Find("buttonAdvertisment1", true)[0];
ba.FadeOut(true);
}
It works like a charm, but I don't think this is the right way, is there another way to access the method from the parent class of the other UserControl?
I can't pass it thru a UserControl constructor, the designer breaks down every time.
You have 2 separate user controls which are not aware of each other, which is good and keeps your code loosely-coupled. Now what you are trying to do is to make them somehow know about each other and communicate. Making them aware of each other breaks the loose-coupling and is a bad design.
What I would suggest is creating a 3rd control which will hold the two together and will handle all the communication between them. Each of your original controls will have public events, to which the parent control can subscribe and handle appropriately.
Check mediator pattern for more info: http://en.wikipedia.org/wiki/Mediator_pattern
What you've done is fine - you could do it by exposing events that fired when you click the button in those controls, and then passing references to each other (subscribing to those, writing the code to fade 'this' control).
That might be a bit too much work for a simple solution, however.
What I would say about your solution is that if you were to change the name of control(s) then it stops working. You could instead do:
var ba = this.Parent.Controls.OfType<ButtonAdvertisement>().FirstOrDefault();
That way you're no longer tied to the control name - but the type of the control. You'll need a using System.Linq; in your code file for this to work. Of course, this relies on the fact that there is only ever one other instance of that control type in the parent.
If you're interested in the first solution I mentioned - then this code snippet should help demonstrate:
public class FadeControl {
public event EventHandler Clicked;
public void FadeOut(bool b){
}
public void AttachTo(FadeControl other){
//splitting this operation to a public and private allows us to
//initiate an attach publicly, but then recurse privately without
//causing a stack overflow
AttachToInternal(other);
other.AttachToInternal(this);
}
private void AttachToInternal(FadeControl other){
other.Clicked += Attached_Clicked;
}
protected virtual void Attached_Clicked(object sender, EventArgs e)
{
//fade me out
FadeOut(true);
}
// provides a way for the deriving class to raise the Clicked event
protected void OnButtonClicked(){
if(Clicked != null) Clicked(this, null);
}
}
public class ButtonDiscount : FadeControl {
Button _button;
//omitted: designer code
//this is your handler for the _button clicked event
private void _button_Clicked(object sender, EventArgs e){
//call the base class' OnButtonClicked method - to raise the event
OnButtonClicked();
//TODO: do work.
}
}
//omitted - code for the ButtonAdvertisement class
Once you have that done - in your form, assuming you have _buttonAdvertisement and _buttonDiscount members in your form and after they're initialised - you simply do:
_buttonAdvertisement.AttachTo(_buttonDiscount);
And that will immediately bind both controls to each other.
Note - in response to a comment below - I've made the event handler in FadeControl for another FadeControl's Clicked event protected and virtual - so you can override it.
I am having a rather odd problem with the Gecko Webbrowser control, I have created my own class which inherits off of the Gecko Webcontrol and within the constructor of this I have set an event:
class fooGeckoClass: Gecko.GeckoWebBrowser
{
public fooGeckoClass()
{
this.DomClick += new EventHandler<Gecko.GeckoDomEventArgs>(fooEventFunction);
}
private static void fooEventFunction(Object sender, Gecko.GeckoDomEventArgs e)
{
((Gecko.GeckoWebBrowser)sender).Navigate("www.foo.com");
}
}
I am using three of these controls in a manually created UserControl, the controls are loaded in dynamically at start up from a config file and added the the UserControl controls collection. When clicking on any of the three controls, all three will navigate to "www.foo.com" away from there original site. I had a look at:
e.StopPropagation();
Which specifies that it stops further propagation of events during an event flow, however it does also specify that it will handle all events in the current flow, I believe the events must have already been given to the controls before this has a chance to stop it as the the three controls will still fire the event. I also tried e.Handled = true to no avail. Has anyone encountered this problem before and have any kind of solution to make it only fire on the control that was clicked on?
EDIT:
It may be worth showing how the controls are added to the form seeing as this must be where the problem is occurring (it does not happen if the controls are just placed in a user control in a small test app).
private void fooUserControl_Load(object sender, EventArgs e)
{
if (!this.DesignMode)
{
for (int iControls = 0; iControls < geckObs.Count(); iControls ++)
{
fooGeckoClass geckControl = new fooGeckoClass();
this.Controls.Add(geckControl );
break;
}
}
}
Odd answer but I seem to have resolved the issue, DomClick was being called at first run, changing to DomMouseClick or DomMouseUp has completely resolved the issue. I assume DomClick must be an event unto itself as it also doesn't use the GeckoDomMouseEventArgs but the regular GeckoEventArgs.
EDIT:
To add to this, the site I was going to was actually calling DomClick when it had finished loading hence the reason it was being called at start up across all three browsers.
Suppose, on Page_Load() of a page (WebForms) that I create this Control :
HtmlGenericControl optionBox = new HtmlGenericControl("div");
optionBox.Attributes["class"] = "class_1";
Than, a use will recall the page using a LinkButton. On the method called from this button, I change the class of my previous div :
protected void cmdCerca_Click(object sender, EventArgs e)
{
...
div.Attributes.Add("class", "class_2");
...
}
Well, if I watch on the rendered result, I'll see that the class of the div have been changed.
This means that, in the next call to this page (from this context, example calling cmdCerca_2_Click), that object will be recovered from the View, getting class_2, not class_1.
But, this doesnt happens if, at the end of cmdCerca_Click, I call the same page with Response.Redirect(). Seems that the View will be lost.
Why? And how can I fix it?
Hope the question is clear.
You need to add the controls in the page init event, rather than load, in order to get them into the control tree.
You must be recreating this control on every postback? In this case, your default class will be set every time.
Created a user control.
Within user control, I have a simple control, like a Literal, in the markup.
In the user control's Page_Load, I attempt to change a property, like Text, on control created in the markup.
Control is null.
What in the world am I missing?
(Begin rant: I am doing all these fancy things with login systems and dynamically adding/modifying controls on the fly with AJAX, etc, but I can't change an f'n static control's property! I can't even Google such a simple problem without finding something else! In the past, I had to dynamically generate the whole bloody page to avoid this idiotically simple problem. End rant.)
Page.LoadControl() has two overloads, one accepts a Virtual Path, the other accepts a Type.
Sometimes, when using the Type version overload, you get this kind of behaviour.
When possible, try to use the Virtual Path version of LoadControl.
Edit: as an FYI, this is because the actual Type of a User Control is not what you would expect it to be. ASP.NET kind of 'wraps' the Type of the User Control.
I figured out a way after analyzing the order a page is executed (http://msdn.microsoft.com/en-us/library/ms178472.aspx).
protected void Page_Init(object sender, EventArgs e)
{
literalGameName.Text = myGame.Name;
}
Init happens after controls have been made, but not after the page is done loading control-stuff.
I know this is an old one, but wanted to chime in on how I fixed a similar issue I was having. I have a usercontrol with an asp:Panel on it that I was trying to set the visibility off during the Page_Load, but the control was coming up null. I then noticed that my Page_Load definition looked like this:
protected void Page_Load(object sender, EventArgs e)
{
_myControl.visible = true;
}
When in fact, I needed the definition to look like this:
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
_myControl.visible = true;
}
Doing the override fixed the issue.
I am trying to create a popup which will be used to select a month/year for a textbox. I have kind of got it working but however when I try and read from the textbox when I Submit the form it returns an empty string. However visually on the page I can see the result in there when I click the Done button which can be seen in the screenshot.
http://i27.tinypic.com/2eduttx.png - is a screenshot of the popup
I have wrapped the whole textbox/popup inside a Web User Control
Here is the code of the control
Code Behind
ASP Page
and then read from the Textbox on the button click event with the following
((TextBox)puymcStartDate.FindControl("txtDate")).Text
Any suggestions of how to fix the problem?
You may need to read the form posted value rather than the value from the view state. I have the following methods in my code to handle this.
The below code just grabs the values in the request headers (on post back) and sets/updates the controls. The problem is that when using the ASP.NET Ajax controls, it doesn't register an update on the control, so the viewstate isn't modified (I think). Anyways, this works for me.
protected void btnDone_Click(object sender, EventArgs e)
{
LoadPostBackData();
// do your other stuff
}
// loads the values posted to the page via form postback to the actual controls
private void LoadPostBackData()
{
LoadPostBackDataItem(this.txtYear);
LoadPostBackDataItem(this.txtDate);
// put other items here if needed
}
// loads the values posted to the page via form postback to the actual controls
private void LoadPostBackDataItem(TextBox control)
{
string controlId = control.ClientID.Replace("_", "$");
string postedValue = Request.Params[controlId];
if (!string.IsNullOrEmpty(postedValue))
{
control.Text = postedValue;
}
else
{
control.Text = null; // string.Empty;
}
}