i added ascx control in tab control with C# codes. if you click any tabs. ASCX control load. tab control in update pane. Alos ASCX control includes button if you click button you can add some value to database but ASCX disappear. i think that it is reloaded. How can i solve it?
i loaded ascx control if i click tab control. i have a button on ASCX. i clicked button ASCX disapper..
protected void ASPxPageControl1_ActiveTabChanged(object source,
DevExpress.Web.ASPxTabControl.TabControlEventArgs e)
{
if (ASPxPageControl1.ActiveTabPage.Name == "Ali Sp. Reqs")
PhAliSpReqs.Controls.Add(UserControlHelper.LoadControl(this.Page, "~/EngWebUserControl/AliSpReqs.ascx"));
else if (ASPxPageControl1.ActiveTabPage.Name == "Test")
PhTest.Controls.Add(UserControlHelper.LoadControl(this.Page, "~/EngWebUserControl/Test.ascx"));
ASCX:
public partial class Test : System.Web.UI.UserControl
{
protected void Page_Load(object sender, EventArgs e)
{
}
public void Button1_Click(object sender, EventArgs e)
{
if (txtTest.Text != String.Empty)
{
Label1.Text = "Hello!";
}
else
Label1.Text = "Error";
}
}
if i clicked tab EVERY THING IS GOOD. But click button on ascx. ASCx control disappear. How can i solve it!!!
If you add controls programmatically in code, every post-back operation needs to re-create the same controls (e.g. during Page_Load) to process the post-back event (in your case, the Save button)
Dynamically added controls have no object reference variable in the codebehind class. They appear only in the control collection of the containing control, i.e. the Page.Controls collection. When the page is posted back to the server as a result of user interaction a new instance of the codebehind class is instantiated, and all the variables of the class is set with values from the ViewState. see here
Related
i have a problem with user control.
i create it dynamically on my aspx page after clicking on a button:
protected void btnAddRules_Click(object sender, EventArgs e)
{
RuleProperty Control = (RuleProperty)LoadControl("RuleProperty.ascx");
MyPanel.Controls.Add(Control);
}
when i click on a button of my user control, the button event wont fire and the user control will disappear. here is the button event:
protected void btnAdd_Click1(object sender, EventArgs e)
{
WowzaRule rule = GetRuleFromGUI();
RuleList.Add(rule);
//Session["RuleList"] = RuleList;
//List<WowzaRule> test = new List<WowzaRule>();
SaveToXMLFiles(txtdbnum.Text, RuleList);
}
i understand that after pressing the button on mypage the usercontrol is released and if its not created on pag_init or page Load it wont stay, but i need to create it on my button click event and find a way for it not to disapper.
thanks in advance, Daniel
You might have to add an event handler that it can fire the click event and call your delegate
Control.Click += btnAdd_Click1;
Dynamically created controls, once added, have to be on a page on every page load in order to work correctly. What happens in your case:
RuleProperty is added after the button click
Page loads with this control
User clicks on the button within RuleProperty
Control is not added to the control tree during the page load (corresponding code is only in the button click handler, and that button was not clicked)
ASP.NET does not know which control triggered the event, so the event is not processed
To go around this issue you need to add you control on every page loading, for example using some flag stored in ViewState:
protected void Page_Load(object sender, EventArgs e)
{
if (ViewState["AddRuleProperty"] != null && (bool)ViewState["AddRuleProperty"])
{
AddRulePropertyControl();
}
}
protected void btnAddRules_Click(object sender, EventArgs e)
{
AddRulePropertyControl();
ViewState["AddRuleProperty"] = true;
}
private void AddRulePropertyControl()
{
RuleProperty Control = (RuleProperty)LoadControl("RuleProperty.ascx");
MyPanel.Controls.Add(Control);
}
Update.
If you want to remove the control from the page later on in the control's click handler, you need to remove corresponding ViewState key. This is not possible from the control directly, since property Page.ViewState is protected, and also this would have created an unwanted dependency.
What seems as the right way to do this is to subscribe to the very same event from the Page (you might need to make this event visible from the controller) and reset the key in there. Like this:
private void AddRulePropertyControl()
{
RuleProperty Control = (RuleProperty)LoadControl("RuleProperty.ascx");
Control.ButtonClick += RuleProperty_ButtonClick;
MyPanel.Controls.Add(Control);
}
private void RuleProperty_ButtonClick()
{
ViewState["AddRuleProperty"] = false;
}
Please note that event name here is not real, this is just a sketch of what can be done.
I have a web form which dynamically loads controls upon selection in combobox(devexpress). I have the following code on main form
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
}
if (Session["_active_control"] != null)//persist control on postbacks
{
Control cntrl = Session["_active_control"] as Control;
pnl_main.Controls.Clear();
pnl_main.Controls.Add(cntrl);
}
}
protected void cmb_control_SelectedIndexChanged(object sender, EventArgs e)
{
Control cntrl= Page.LoadControl("~/" + cmb_control.SelectedItem.Value);
pnl_main.Controls.Clear();
pnl_main.Controls.Add(cntrl);
Session["_active_control"] = cntrl;
}
also I have a user control having three Textboxes and a button having code
protected void btn_save_Click(object sender, EventArgs e)
{
lbl.Text = ASPxTextBox1.Text + "<br>" + ASPxTextBox2.Text + "<br>" + ASPxTextBox3.Text;
}
My problem is that the save button of user control is not firing if i load it dynamically (I have checked using breakpoints and also the code shown above. however it runs smoothly if I use it statically.(i.e. by dragging in design mode)
You are right that you have to persist the control across postbacks.
However the Page Load event is too late to add back your controls. Do this on the Init event of your page and you should be good. To receive a postback event, the control should be present when ProcessPostData(called before PreLoad) is called.
Also for textboxes you will want to receive the values entered by the user. This too happens on ProcessPostData, if you add you control after that, you will not receive the values entered by the user.
Refer: ASP.NET Page Life Cycle
hey i found the solution
instead on creating the controls in combobox_selectedindexchanged i put my control creation code on Pageload based in combobox.selectedindex i.e.
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
if (cmb_control.SelectedItem != null)
{
Control cntrl = Page.LoadControl("~/" + cmb_control.SelectedItem.Value);
cntrl.ID = "_new_ctrl" + cmb_control.SelectedItem.Value;
pnl_main.Controls.Clear();
pnl_main.Controls.Add(cntrl);
}
}
see Button click event not firing within use control in ASP .Net
I am aware that many of the content pages will create textBox controls with lets say txtCustomerName. And if this is found I need to update the value from session. In this particular case I can not move these controls to master page.
How do you access page controls from master page. And in which event of page life cycle should we attempt to do this ?
You can find in any Event you would like to, like in this example I am showing you on Button Click Event
protected void Button1_Click(object sender, EventArgs e)
{
TextBox TextBox1 = ContentPlaceHolder1.FindControl("TextBox1") as TextBox;
if (TextBox1 != null)
{
Label1.Text = TextBox1.Text;
}
}
Good morning everybody.
I have a question connected with controls and event handling. Lets say I want to create a LinkButton.
protected void loadLinkButton()
{
ContentPlaceHolder content = (ContentPlaceHolder)this.Master.FindControl("MainContent");
LinkButton lnk = new LinkButton();
lnk.ID = "lnikBtn";
lnk.Text = "LinkButton";
lnk.Click += new System.EventHandler(lnk_Click);
content.Controls.Add(lnk);
}
Here is the event handler:
protected void lnk_Click(object sender, EventArgs e)
{
Label1.Text = "ok!";
}
If I run the loadLinkButton function inside Page_Load everything is ok. But when I try to run the loadLinkButton by clicking simple button, link button is created but event is not handled.
protected void Button1_Click(object sender, EventArgs e)
{
loadLinkButton();
}
I there any way to solve it? Or loadLinkButton must always regenerated on Page_Load, Page_init etc.
When working with dynamic controls, I always add the control in Page_Init, because viewstate loading will happen right after Init. If you add it to Page_Load, there is a chance that you will lose viewstate. Just make sure you provide a unique control ID.
It is important to know how ASP.Net determines which events to invoke. The source of each event is passed using a hidden field:
<input type="hidden" name="__EVENTTARGET" value="" />
Whenever the page loads, it pulls in the source of the event from that field and then determines which event to invoke. Now this all works great for controls added through markup because the entire control tree is regenerated on every request.
However, your control was only added once. When a Postback occurs, your control no longer exists as a Server control in the tree, and therefore the event never fires.
The simply way to avoid this is to make sure your Dynamic Controls are added every time the page loads, either through the Page_Init event, or the Page_Load event.
You are right. This is the expected behavior. Page_Load and Page_Init would be the events where you should be adding it.
That would be because when you click your dynamically generated linkbutton, you do a postback to the server. There you do an entirely new pageload, but your original buttonclick (that generates the link) never happened now, so the linkbutton is never made, and the event can not be thrown.
An alternative is to add the linkbutton you add dynamically, to your page statically, with Visible = false. And when you click the other button, make it visible.
I am not exactly sure what problem you are facing but you should put the dynamic controls code in Page_Init as suggested by #johnofcross:
public partial class WebForm1 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Page_Init(object sender, EventArgs e)
{
CreateControls();
}
private void CreateControls()
{
var lb = new LinkButton();
lb.Text = "Click Me";
lb.Click += lb_Click;
ph.Controls.Add(lb);
ph.DataBind();
}
void lb_Click(object sender, EventArgs e)
{
lblMessage.Text = "Button is clicked!";
}
}
In one of my projects I need to build an ASP.NET page and some of the controls need to be created dynamically. These controls are added to the page by the code-behind class and they have some event-handlers added to them. Upon the PostBacks these event-handlers have a lot to do with what controls are then shown on the page. To cut the story short, this doesn't work for me and I don't seem to be able to figure this out.
So, as my project is quite involved, I decided to create a short example that doesn't work either but if you can tweak it so that it works, that would be great and I would then be able to apply your solution to my original problem.
The following example should dynamically create three buttons on a panel. When one of the buttons is pressed all of the buttons should be dynamically re-created except for the button that was pressed. In other words, just hide the button that the user presses and show the other two.
For your solution to be helpful you can't statically create the buttons and then use the Visible property (or drastically change the example in other ways) - you have to re-create all the button controls dynamically upon every PostBack (not necessarily in the event-handler though). This is not a trick-question - I really don't know how to do this. Thank you very much for your effort. Here is my short example:
From the Default.aspx file:
<body>
<form id="form1" runat="server">
<div>
<asp:Panel ID="ButtonsPanel" runat="server"></asp:Panel>
</div>
</form>
</body>
From the Default.aspx.cs code-behind file:
using System;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace DynamicControls
{
public partial class _Default : Page
{
protected void Page_Load(object sender, EventArgs e)
{
AddButtons();
}
protected void AddButtons()
{
var lastClick = (string) Session["ClickedButton"] ?? "";
ButtonsPanel.Controls.Clear();
if (!lastClick.Equals("1")) AddButtonControl("1");
if (!lastClick.Equals("2")) AddButtonControl("2");
if (!lastClick.Equals("3")) AddButtonControl("3");
}
protected void AddButtonControl(String id)
{
var button = new Button {Text = id};
button.Click += button_Click;
ButtonsPanel.Controls.Add(button);
}
private void button_Click(object sender, EventArgs e)
{
Session["ClickedButton"] = ((Button) sender).Text;
AddButtons();
}
}
}
My example shows the three buttons and when I click one of the buttons, the pressed button gets hidden. Seems to work; but after this first click, I have to click each button TWICE for it to get hidden. !?
I think that you have to provide the same ID for your buttons every time you add them like this for example (in first line of AddButtonControl method):
var button = new Button { Text = id , ID = id };
EDIT - My solution without using session:
public partial class _Default : Page
{
protected override void OnPreInit(EventArgs e)
{
base.OnPreInit(e);
AddButtons();
}
protected void AddButtons()
{
AddButtonControl("btn1", "1");
AddButtonControl("btn2", "2");
AddButtonControl("btn3", "3");
}
protected void AddButtonControl(string id, string text)
{
var button = new Button { Text = text, ID = id };
button.Click += button_Click;
ButtonsPanel.Controls.Add(button);
}
private void button_Click(object sender, EventArgs e)
{
foreach (Control control in ButtonsPanel.Controls)
control.Visible = !control.Equals(sender);
}
}
You need to make sure that your dynamic controls are being added during the Pre_Init event.
See here for the ASP.NET Page Lifecycle: http://msdn.microsoft.com/en-us/library/ms178472.aspx
When adding events you need to do it no later than the Page_Load method and they need to be added every single request, ie you should never wrap event assignment in a !IsPostBack.
You need to create dynamic controls ever single request as well. ViewState will not handle the recreation on your behalf.
One thing I notice is that when you click a button you are invoking AddButtons() twice, once in the Page_Load() and once in the button_Click() method. You should probably wrap the one in Page_Load() in an if (!IsPostBack) block.
if (!IsPostBack)
{
AddButtons();
}
AFAIK, creating of controls should not be placed in Page_Load but in Page_PreInit (ViewState and SessionState is loaded before Page_Load but after Page_PreInit).
With your problem, I would suggest to debug the AddButtons function to find out what exactly (and when) is stored in Session["ClickedButton"]. Then, you should be able to figure out the problem.
the controls that are added dynamically are not cached so this migth me one of your problems