I want to keep selected item after page reload:
Excerpt from .aspx:
<asp:DropDownList ID="MyDropDown" runat="server" AutoPostBack="true"
onselectedindexchanged="MyDropDown_SelectedIndexChanged">
</asp:DropDownList>
Exerpt from .cs in page_load
if (!IsPostBack)
{
PopulateDropDownList();
}
with
private void PopulateDropDownList()
{
MyDropDown.Items.Add("1");
MyDropDown.Items.Add("2");
}
protected void MyDropDown_SelectedIndexChanged(object sender, EventArgs e)
{
Response.Redirect(Request.RawUrl);
}
Response.Redirect refresh the page and you will loose view state that will have selected index. You can put the selected index in session before redirecting.
protected void MyDropDown_SelectedIndexChanged(object sender, EventArgs e)
{
Session["MyDropDownSelectedIndex"] = MyDropDown.SelectedIndex.ToString();
Response.Redirect(Request.RawUrl);
}
You need to populate the drop down list in the Page init event. If you do that during Page load event the view state cannot be restored correctly (because the drop down list is not populated before Page load event) so the on selected index changed event cannot be fired.
EDIT: you may want to cache the data which populate the drop down list to save some around trip to the database. I think you do not need to redirect in the on selected index changed event too.
Related
I have created one page.In that page,I wrote one javascript function for displaying character count,when user enter something in textbox.
protected void Page_Load(Object sender, EventArgs e)
{
TextBox1.Attributes.Add("onkeyup", "DisplayCharCount()");
}
First time pageload,textbox is blank. Textbox does not have autopostback== true.After
pageload,user enter text into textbox.This time page is not loaded again.So when this function get called?
Page_Load will call everytime a page reloaded. so onkeyup will bind to the textbox everytime a page reloaded.
When this function get called?
This event is triggered when the user releases a Key while typing on TextBox1.
You can also bind it for the first time only:
protected void Page_Load(Object sender, EventArgs e)
{
if(!IsPostBack)
{
TextBox1.Attributes.Add("onkeyup", "DisplayCharCount()");
}
}
Or you can also bind it directly as:
<asp:TextBox ID="TextBox1" runat="server" TextMode="MultiLine" onkeyup="DisplayCharCount()">
</asp:TextBox>
The Page_Load method is called every time a user requests the page. The DisplayCharCount method is called whenever a user pressed a key (that is, release the key) in the TextBox1 element.
I have a feeling I'm missing something really obvious, I'm not able to capture the selected value of my DropDownList; the value renaubs the first item on the list. I have set the DropListList autopostback property to true. I have a SelectedIndexChangedEvent which is pasted below. This is NOT on the master page.
protected void ddlRestCity_SelectedIndexChanged(object sender, EventArgs e)
{
if (IsPostBack)
{
r_city = ddlRestCity.SelectedValue.ToString();
}
}
Here is the DropDownList control:
<asp:DropDownList ID="ddlRestCity" runat="server"
Width="100px" AutoPostBack="True"
onselectedindexchanged="ddlRestCity_SelectedIndexChanged">
</asp:DropDownList>
Thanx in advance for your help!
My off the cuff guess is you are maybe re-populating the list on a post back and that is causing the selected index to get reset.
Where is your DataBind() call? Are you checking !IsPostBack before the call? For example:
protected void Page_Load(object sender, EventArgs e) {
if (!IsPostBack) {
ddlRestCity.DataSource = ...;
ddlRestCity.DataBind();
}
}
Explanation: If you don't check for !IsPostBack before DataBind(), the list will re-populate before SelectedIndexChanged is fired (because Page.Load fires before child events such as SelectedIndexChanged). When SelectedIndexChanged is then fired, the "selected item" is now the first item in the newly-populated list.
What is r_city?
If it's a textbox, then you need to do something like r_city.text = ...
Also -- you might consider removing your postback check. Usually, that's most useful in the page.onload event, and usually, you're checking for if NOT ispostback...
For a "dashboard" module I need to dynamically load user controls based on criteria as the user enters the page (role, etc). The problem is that the events are not being fired at all from the controls
As I understand it I need to load the controls in the OnPreInit method of the dashboard page, however I cannot get a reference to the Placeholder control at this point of initialization (i.e. I get a NullReferenceException); trying to load the Placeholder dynamically via Page.FindControl gives me, ironically, a StackOverflowException.
I've tried loading the controls in PreRender and OnInit as well but the events in the controls are not wired up properly and will not fire.
The code is basically this:
// this does not work; if I try to access the placeholder control itself
// ("phDashboardControls") I get a NullReferenceException, if I try
// Page.FindControl("phDashboardControls") I get a StackOverflowException
protected override void OnPreInit(EventArgs e)
{
base.OnPreInit(e);
Control ph = Page.FindControl("phDashBoardControls"); // Placeholder
if (ph != null)
{
// GetControlsToLoad just instantiates the controls and returns
// an IList<Control>. Eventually it will have logic to
// determine which control needs to be loaded based on user role etc.
foreach (Control control in GetControlsToLoad())
{
ph.Controls.Add(control);
}
}
}
// IModularControl is a custom interface defining a single
// Initialize method to set up a control...
private void Page_Load(object sender, EventArgs e)
{
foreach (Control control in this.phDashboardControls.Controls)
{
if (control is IModularControl)
((IModularControl)control).Initialize(this.CompanyID);
}
}
I've successfully loaded controls dynamically in Page_Load before. The only thing I found I had to be careful of was to ensure that if I did a postback, the same controls were loaded in subsequent page_load to ensure that the view state didn't get corrupted... all events etc worked as expected. In my case the controls flow ended up something like this:
page_load - load control a
(do something which causes postback and event x to fire)
page_load - make sure you load control a
event_x - clear control a, load control b
(do something which causes postback)
page_load - make sure you load control b
...
it meant loading controls you fully intented discarding, but was the only way I could find to not corrupt the viewstate...
If you have a page with PlaceHolder1 and Label1 in it, then the following code causes the button click event to fire just fine:
protected void Page_Load(object sender, EventArgs e)
{
var dynamicButton = new Button() { Text = "Click me" };
dynamicButton.Click +=new EventHandler(dynamicButton_Click);
PlaceHolder1.Controls.Add(dynamicButton);
}
void dynamicButton_Click(object sender, EventArgs e)
{
Label1.Text = "Clicked button";
}
Behaves the same with a user control:
WebUserControl ascx:
<%# Control Language="C#" AutoEventWireup="true" CodeFile="WebUserControl.ascx.cs" Inherits="WebUserControl" %>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:Button ID="Button1" runat="server" Text="Click Me" onclick="Button1_Click" />
WebUserControl code behind:
protected void Button1_Click(object sender, EventArgs e)
{
Label1.Text = "Clicked Button";
}
parent control that loads the child control:
protected void Page_Load(object sender, EventArgs e)
{
var dynamicControl = Page.LoadControl("~/WebUserControl.ascx");
PlaceHolder1.Controls.Add(dynamicControl);
}
Just FYI the issue had to do with validation; the events weren't firing properly because some of the validation controls (there were a ton) weren't configured to only apply to that control.
I have a user control that contains a repeater. We have added some paging and sorting into the user control and it all works well.
What I need now is a nice way to catch the OnItemDataBound event of the inner repeater and then bubble it up to be accessible directly from the user control from within the page.
We have tried catching it and then declaring it in the user control but it just won't work. Has anyone ever tried this before and if so could I see some code to suggest how it might look.
Many Thanks
Try something like this:
<asp:Repeater ID="Repeater1" runat="server"
onitemdatabound="Repeater1_ItemDataBound">
</asp:Repeater>
Then subscribe to the event, and publish another event with the same data
protected void Repeater1_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
OnInnerRepeaterItemDataBound(sender,e);
}
public event EventHandler<RepeaterItemEventArgs> InnerRepeaterItemDataBound;
public void OnInnerRepeaterItemDataBound(object sender, RepeaterItemEventArgs e)
{
if (InnerRepeaterItemDataBound != null)
InnerRepeaterItemDataBound(sender, e);
}
That should do it, now you can subscribe to the user control Event InnerRepeaterItemDataBound that would be fired when your inner Repeater1_ItemDataBound fire.
I have a user control, which is added to another user control. The nested user control is built up of a GridView, an image button and a link button. The nested user control is added to the outer control as a collection object based upon the results bound to the GridView.
The problem that I have is that my link button doesn't work. I click on it and the event doesn't fire. Even adding a break point was not reached. As the nested user control is added a number of times, I have set image button to have unique ids and also the link button. Whilst image button works correctly with its JavaScript. The link button needs to fire an event in the code behind, but despite all my efforts, I can't make it work. I am adding the link button to the control dynamically. Below is the relevant code that I am using:
public partial class ucCustomerDetails : System.Web.UI.UserControl
{
public event EventHandler ViewAllClicked;
protected override void CreateChildControls( )
{
base.CreateChildControls( );
string strUniqueID = lnkShowAllCust.UniqueID;
strUniqueID = strUniqueID.Replace('$','_');
this.lnkShowAllCust.ID = strUniqueID;
this.lnkShowAllCust.Click += new EventHandler(this.lnkShowAllCust_Click);
this.Controls.Add(lnkShowAllCust);
}
protected override void OnInit (EventArgs e)
{
CreateChildControls( );
base.OnInit(e);
}
protected override void OnLoad(EventArgs e)
{
base.EnsureChildControls( );
}
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack)
{
CreateChildControls( );
}
}
protected void lnkShowAllCust_Click(object sender, EventArgs e)
{
this.OnCustShowAllClicked(new EventArgs ( ));
}
protected virtual void OnCustShowAllClicked(EventArgs args)
{
if (this.ViewAllClicked != null)
{
this.ViewAllClicked(this, args);
}
}
}
I have been stuggling with this problem for the last 3 days and have had no success with it, and I really do need some help.
Can anyone please help me?
My LinkButton wasn't firing it's Click event, and the reason was I had its CausesValidation property set to True. If you don't want the link to validate the form, be sure to set this to False.
Try adding your click event to the linkbutton tag:
<asp:LinkButton runat="server" OnClick="linkShowAllCust_Click" />
Or adding it to your Page_Load:
Page_Load(object sender, EventArgs e)
{
this.lnkShowAllCust.Click += new EventHandler(this.lnkShowAllCust_Click);
}
Is the usercontrol within the gridview? If so register the event handler on the gridview's onrowcreated event.
It appears that you have a viewstate issue. Because the control isn't there when the viewstate is loaded the application doesn't know how to hook up the event to be fired. Here is how to work around this.
You can actually make your app work like normal by loading the control tree right after the loadviewstateevent is fired. if you override the loadviewstate event, call mybase.loadviewstate and then put your own code to regenerate the controls right after it, the values for those controls will be available on page load. In one of my apps I use a viewstate field to hold the ID or the array info that can be used to recreate those controls.
Protected Overrides Sub LoadViewState(ByVal savedState As Object)
MyBase.LoadViewState(savedState)
If IsPostBack Then
CreateMyControls()
End If
End Sub
I had the same issue. I had viewstate="false" on the page I was adding the control to. (on the aspx page)