If I make my own custom control, I have to make sure I add all controls in the OnInit, or else postbacks won't work. ProcessPostData is called between Init() and Load(), so if I add my controls in Load(), the post data step has already been done before my control was on the page.
However, if I put a button in an ASP.NET repeater and only bind data to the repeater in Page_Load(), the repeater triggers the ItemCommand event, even though the control was not on the page during Init. How does this work? How do I make my own custom control that adds buttons to the control in Load() or PreRender()?
I want something like this:
public class WrappedButton : WebControl
{
protected override void OnPreRender(EventArgs e)
{
base.OnPreRender(e);
var button = new Button { Text = "Hello" };
button.Click += SomeCommand;
Controls.Add(button);
}
private void SomeCommand(object sender, EventArgs e)
{
Page.Response.Write("This won't get executed");
}
}
Related
I use an ascx user control for manage CRUD o database entity. I reuse this userc control in my aspx page for show in readonly mode the database data of a record on database. The user control have inside a simple FormView and an objectdatasource.
Now, in a aspx page that contains that ascx i have to know, in DATABIND time of the aspx some data of the record of the database that is considerate by the user control. User control are databind after the aspx page, and for this reason i don't have the data. I have to do a select in aspx page on database and after the user control do the same select.
How can i do for optimize this process?
ASCX base events may be fired after your ASPX's base events, but in the whole lifecycle, you can fire your own events.
You could define an Event on your ASCX, make your page register to this event, and then propagate your custom event from your ASCX to your ASPX, with whatever data you need in the arguments
rough example (may not compile) : in the ASCX
public partial YourControl : System.Web.UI.UserControl {
public event EventHandler MyControlDataBound;
public void FireMyControlDataBound()
{
if (MyControlDataBound!= null)
{
MyControlDataBound(this, new EventArgs());
}
}
protected void MyDataBound(object sender, EventArgs e) {
// ......
FireMyControlDataBound();
}
}
and in the ASPX
public partial class MyPage: Page
{
protected void Page_Load(object sender, EventArgs e)
{
yourUserControlInstance.MyControlDataBound += HandleYourDataInYourPage;
}
protected void HandleYourDataInYourPage(object sender, EventArgs e) {
// .. do whatever needed in your page, with your data
// if you have defined a custom Args class that inherits EventArgs, your could collect data here...
}
}
Feel free to create a class that inherits EventArgs to pass data with your event if you need this
You can pass your arguments to your UserContol in init event of your Page
protected override void OnInit(EventArgs e)
{
base.OnInit(e);
var control = (UserControl)this.FindControl("UserControlId");
control.Property = ...;//Pass User Control properties
}
I created a textbox and a submit button in header(User Control) included in a master page
and I want to use that textbox value after clicking submit in my .aspx.vb page.
How can i access that, as the vb page is loaded first and then master page is loading ?
TextBox Val = (TextBox)this.Master.FindControl("TextBoxID");
The best way to communicate from UserControl to Page/MasterPage is using events
The best way to communicate from MasterPage to Page is using events
On this way you don't hardlink UserControls with their Pages/MasterPages and the Page with it's Master.
Add an event to your UserControl that is raised when the user clicks the button, for example:
In UserControl of type MyControl:
public delegate void SubmittedHandler(MyControl ctrl);
public event SubmittedHandler Submitted;
protected void BtnCLick(object sender, EventArgs e) {
Submitted(this);
}
Then add an handler to this event in your MasterPage, handle it and raise the Master's event again:
In Master's codebehind:
public delegate void MyControlSubmittedHandler(MyControl ctrl);
public event MyControlSubmittedHandler ControlSubmitted;
protected void Page_Init(Object sender, EventArgs e) {
this.MyControl1.Submitted += MyControlSubmitted;
}
protected void MyControlSubmitted(MyControl sender) {
ControlSubmitted(sender);
}
Then add an handler to this event to your page:
In your Page:
protected void Page_Init(object sender, EventArgs e) {
((SiteMaster)Master).ControlSubmitted += MasterControlSubmitted;
}
protected void MasterControlSubmitted(MyControl sender){
// do whatever you need to do
}
If you only need to access the TextBox from the page and you don't need to handle the click-event, you could also use properties to achieve this:
add a public property f.e. MyControlText in your UserControl that get/set the TextBox.Text property
add a public property f.e. MyControlText in your Master that get/set your UserControl's MyControlText property
Now you can get/set this property from your page in this way:
((SiteMaster)Master).MyControlText = "Hello World";
Let's say I have a page with my custom UserControl (containing only asp:Literal and some string property) and a button. Now I want to change Literal's text on button click, so I change my control's string property in button clicked event. Like this:
//in aspx
protected void Button1_Click(object sender, EventArgs e)
{
testControl.Text = "triggered";
}
The problem is my Literal remains unchanged because Page_Load event fires first and creates my custom control, then Button_Clicked fires and changes property but as control is already created, it does nothing. This is my control's code behind:
public partial class TestControl : System.Web.UI.UserControl
{
public string Text { get; set; } }
protected void Page_Load(object sender, EventArgs e)
{
lblTest.Text = Text;
}
}
I figured out that if I move any logic in custom control from Page_Load to property setter it will change like intended. Like this:
public string Text { get { return lblTest.Text; } set { lblTest.Text = value; } }
Is there any other (better) way to do this? My real problem involves much more complicated controls than described here, but problems remains the same: on any postback all properties set in event handlers are ignored.
Moving all logic from Page_Load to Page_PreRender solved the problem. Now properties are set before logic executes. I'll wait for other answers to check if there is better solution and if there are any drawbacks of using Page_PreRender.
This video might help: How Do I: Persist the State of a User Control During a Postback
I have created a User Control(Popupcontrol) and in that control i have created a property(PageType) and when i am using the Popupcontrol on the page then i set the property(pagetype) according to the page.
but now there is some problem i have to two button on the page and on the second button click i want to change the pagetype property .So is there any solution for the same.
Based on your comment, it seems you bind the data (PageType property in your question) in the Page_Load event, instead of this it should be done in overrided DataBind method which should be called if the page is not in post back request (otherwise your data will be overwritting in the next Page_Load event as you mentioned in your comments):
protected void Page_Load(object sender, EventArgs e)
{
if(!Page.IsPostBack)
{
DataBind();
}
}
public override void DataBind()
{
PageType = someValue;
}
after this your click handler may looks like:
protected void button2_Clicked(object sender, EventArgs e)
{
PageType = someOtherValue;
}
Are you setting the variable in a page load event? You may need to add:
if (!Page.IsPostback) {
// Code here.
}
I have a blank user control (child) and during Page_Load i create some text boxes and a button. I also add an event to the button.
I then load that user control dynamically from a placeholder in another usercontrol (parent).
Both controls are rendered correctly but when i click on the button, the event isnt fired.
Any ideas on how to handle the event?
Child code:
protected void Page_Load(object sender, EventArgs e)
{
/*... other user controls ..*/
UpdateButton = new LinkButton();
UpdateButton.ID = "buttonid";
UpdateButton.Text = "text";
UpdateButton.Click += new EventHandler(UpdateButton_Click);
this.Controls.Add(UpdateButton);
}
protected override void Render(HtmlTextWriter writer)
{
for (int i = 0; i < this.Controls.Count; i++)
{
this.Controls[i].RenderControl(writer);
}
}
public void UpdateButton_Click(object sender, EventArgs e)
{
//Do stuff
}
Parent code:
protected void Page_Load(object sender, EventArgs e)
{
placeholder.Controls.Clear();
ChildControl uc = (ChildControl)LoadControl("~/UserControls/ChildControl.ascx");
placeholder.Controls.Add(uc);
}
If i use the child control directy (ie without the parent the control) the click event is raised and handled nicely. But when i use the parent control, the debugger wont even hit a breakpoint inside UpdateButton_Click().
Thanks in advance.
I think I know what might be happening. In your parent Page_Load you are calling placeholder.Controls.Clear(); This does what you would imagine and clears the control, including any events that have occurred. What happens when remove this line? Do you get an additional one created on each postback?