Develop Reference

FormView datasource lost on button click in another formview

I want to preface this by saying that I am a beginner to asp.net, especially when it comes to working with the FormView controls. I have searched long and hard and have spent hours debugging this issue.
I have 3 FormViews on one aspx page. Each FormView has its own EditItemTemplate and PagerTemplate with DefaultMode="Edit". I am not using a SqlDataSource, but instead databinding programatically on the PageLoad when if(!Page.IsPostBack) and also calling the databinding method when the PageIndexChanging method is called. The pager template contains a 'Back' and a 'Next' button set with CommandArgument="Prev" and CommandArgument="Next", respectively, and both set with CommandName="Page".
The paging works great on the first FormView. When I hit the back or next button, it pages (i.e. re-binds) appropriately. During the 1st FormView's paging event, I also successfully call the binding methods for the 2nd and 3rd FormView since I want them to bind data that is specific to the page selected in the 1st FormView.
But, when I page back to the first page of the 1st FormView (i.e. PageIndex = 0), and then try to page forward in the 2nd FormView, the datakey for the 1st FormView is null. In fact, the formview1.DataSource is null for the 1st FormView when I try to click a navigation button on the 2nd FormView.
Then, here's where I thought it was weird, ... if I click back a second time on the 1st FormView, THEN the formview1.DataSource is fine, and I can then navigate in the 2nd FormView.
All viewstates for the formviews and the buttons are set to true.
I have tried calling formview1.DataBind() inside formview2's paging event before any paging occurs but no success there. I have also tried setting properties: UseSubmitBehavior="False" and CausesValidation="False" on the paging buttons. Admittedly, I did this without really understanding the behavior but rather implemented after seeing it suggested in solutions for other somewhat related problems.
The templates are rather long since there are many fields in each. But the FormView tags look like this:
<asp:FormView ID="fvHeader" runat="server" DataKeyNames="ObjectID" DefaultMode="Edit" AllowPaging="True" OnModeChanging="fvHeader_ModeChanging" OnPageIndexChanging= "fvHeader_PageIndexChanging">
<EditItemTemplate> ..... </EditItemTemplate> </asp:FormView>
PagerTemplates:
<PagerSettings Mode="NextPrevious" />
<PagerTemplate>
<span class="labels">Page: <%#fvHeader.PageIndex+1%> of <%#fvHeader.PageCount %></span>
<asp:Button ID="btnBack" runat="server" CommandArgument="Prev" CommandName="Page" CssClass="btnHdr" Text="<< Back" />
<asp:Button ID="btnNext" runat="server" CommandArgument="Next" CommandName="Page" CssClass="btnHdr" Text="Next >>" /> </PagerTemplate>
Note that 'fvHeader' is what I'm calling 'formview1' for simplicity in my question.
Back/Next buttons C# code and databinding the 1st formview:
protected void fvHeader_PageIndexChanging(object sender, FormViewPageEventArgs e)
{
fvHeader.PageIndex = e.NewPageIndex;
bindFV_Initial();
//rebind fvSub1 (2nd formview) to get the 1st obs of the newly selected header record
fvSub1.ChangeMode(FormViewMode.Edit);
fvSub1.PageIndex = 0;
bindSub1_Initial();
//rebind 2nd subform
fvSub2.ChangeMode(FormViewMode.Edit);
fvSub2.PageIndex = 0;
bindSub2_Initial();
}
private void bindFV_Initial()
{
if (conn.State == ConnectionState.Open)
{
conn.Close();
}
conn.Open();
if (dtEOS == null || dtEOS.Rows.Count == 0)
{
sqlda = new SqlDataAdapter("USE dbWEF SELECT * FROM tblHeader WHERE [UserID] = '" + Session["User"] + "' AND [ProjectName] = '" + Session["Project"] + "'", conn);
sqlda.Fill(dtEOS);
}
fvHeader.DataSource = dtEOS;
fvHeader.DataBind();
conn.Close();
if (dtEOS.Rows.Count > 0)
{
fillDD_fvHeader(); //Fill dropdowns and databind ddls
}
}
}
Below is the error message I receive when I attempt to navigate the 2nd formview.
Error in: bindSub1_Initial.
System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
at System.Collections.ArrayList.get_Item(Int32 index)
at System.Collections.Specialized.OrderedDictionary.get_Item(Int32 index)
at System.Web.UI.WebControls.DataKey.get_Item(Int32 index)
at RenewableEnergyDataEntry.Forms.EagleObservationSurvey.bindSub1_Initial()
During debugging, I find that this error occurs right when the 2nd formview is being binded because the datatable is empty which is a result of it needing the datakey from formview1 to pull the correct data, which again, is null because formview1's datasource goes to null. But clicking formview's back button one more time, refills and KEEPS the datasource, thereby allowing formview2 to fill and navigate perfectly. So strange...

I suggest you simplify you code.
more than likely you are creating conflicts with the view state.
We can't see where and how your dataSource: (dtEOS) is being defined.
But I am going to guess that it's being reset conditionally on a call back.
This is a common problem in ASP.net (conflict with view sate and /or databinding).
Try using a grid instead of a formview and it will handle the paging much more gracefully without needing a postback and data rebind.

ASP.NET populate lists referencing each other on selected index change

I have an ASP.NET control with three listboxes: LBParent, LBChild1 and LBChild2.
LBParent has to be filled programmatically. I do this in Page_Load.
When the user selects a value in LBParent, I want to fill both LBChild1 and LBChild2 with some data, programmatically. The children lists must also keep track of their selected value.
Basically, the parent list is a list of users, the first list is a list of permissions the user has, the second list is a list of permissions the user doesn't have.
My plan is to add two buttons to move permissions between the two lists.
Unfortunately, I cannot get this to work properly.
If I populate the parent list in Page_Load, the selected index seems to reset. I used ViewState to save the index... but this seems to require an additional refresh, because it doesn't update after the PostBack. This is not acceptable.
If I populate the children listboxes on the OnParentSIC event, there is no way I can keep track of their selected index. The OnChildXSIC events never fire, because the listboxes get repopulated "too soon". (?)
How can I get this to work as intended? Maybe there is a better solution but I'd really like to understand how to get this solution to work, as I can't see a possible solution at the moment.
Control.ascx
<%# Control Language="C#" AutoEventWireup="true" EnableViewState="True" CodeBehind="..." Inherits="..." %>
<form runat="server">
<asp:ListBox ID="LBParent" runat="server" CssClass="form-control"
AutoPostBack="true" OnSelectedIndexChanged="OnParentSIC" />
<asp:ListBox ID="LBChild1" runat="server" CssClass="form-control"
AutoPostBack="true" OnSelectedIndexChanged="OnChild1SIC" />
<asp:ListBox ID="LBChild2" runat="server" CssClass="form-control"
AutoPostBack="true" OnSelectedIndexChanged="OnChild2SIC" />
</form>
Control.ascx.cs
protected void Page_Load(object sender, EventArgs e)
{
// Populate parent
for(...) LBParent.Items.Add(...);
}

The Onchange-event fires, but before that the OnLoad fires.
So:
The user clicks on an selection
A postback is triggered
At the server the Onload fires (and rebuilds the list)
The OnSelectedIndexChanged fires (which lost the selection by now)
So I would try to save the current-selected-index before you rebuild the list (in the Onload).
If you restore it later on while you are in the same 'postback' you can save it in a simple variable. No need to store in a Viewstate or Session.

use Like this
If You are on the Same Page then You can Use ViewState/Hidden Fields
to Maintain States
First Time Adding ListItem on PageLoad Use Like this
protected void Page_Load(object sender, EventArgs e)
{
if(!Page.IsPostBack)
{
AddListItems();
}
}
Protected Void AddListItems()
{
// Populate parent
for(...) LBParent.Items.Add(...);
for(...) SecondList.Items.Add(...);
for(...) ThirdList.Items.Add(...);
}

RadComboBox CheckBoxes mulitselect get values of CheckedItems

I have master page named MPHome.master contains a RadComboBox here is the code of
<telerik:RadComboBox CheckBoxes="true" EnableCheckAllItemsCheckBox="true" ID="TaskID" runat="server" Height="100" Width="150" EmptyMessage="Select a Task"
EnableLoadOnDemand="true" OnClientItemsRequesting="OnClientItemsRequesting" WebServiceSettings-UseHttpGet="true" ShowMoreResultsBox="true" EnableVirtualScrolling="true">
<WebServiceSettings Method="GetTasks" Path="~/ProjectDropDownWebService.asmx" />
</telerik:RadComboBox>
Now this combo works fine it fills values from webservice and also shows checkboxes on it.Now what I do is I inherit this master page to Default.aspx page and inside button of submit in default page I have used this code
protected void btnViewAllTask_Click(object sender, EventArgs e)
{
RadComboBox TaskID = (RadComboBox)Master.FindControl("TaskID");
var selectedtask = TaskID.CheckedItems;
}
This selectedtask returns me count of zero either i have selected all the records on it.

As far as I know. You are trying to use the CheckBoxes along with Load On Demand feature which is not a supported scenario with telerik RadComboBox with checkboxes=true.
Please find more details about this topic here.

GridView not updating from SelectedIndexChange event of a DropDownList within an UpdatePanel

My problem:
An UpdatePanel holds a DropDownList and a GridView. The GridView populate baseds on a value that is stored in a Label and a value that is selected from a DropDownList. It does NOT populate on PageLoad; it only populates when a query string is present or when a button is pressed, so there is no code in the !IsPostBack. The GridView is populated with the initial SelectedValue of the DropDownList, and I want the GridView to repopulate when the SelectedValue of the DropDownList changes.
The thing is... IT DOES CHANGE! But only once. The GridView initially populates with data using the value of the default SelectedValue of the DropDownList. When the SelectedValue is changed, the data in the GridView changes. But only once. After changing the DropDownList value the second time or more, nothing happens.
<asp:UpdatePanel runat="server" ID="theUpdatePanel" UpdateMode="Conditional" ChildrenAsTriggers="True">
<ContentTemplate>
<asp:DropDownList runat="server" ID="theDropDownList" OnSelectedIndexChanged="theDropDownList_OnSelectedIndexChanged" EnableViewState="true" AutoPostBack="true" />
<asp:GridView ID="theGridView" runat="server" AutoGenerateColumns="False">
<Columns>
...
</Columns>
</asp:GridView>
</ContentTemplate>
</asp:UpdatePanel>
theUpdatePanel's UpdateMode is Conditional, so it updates when its children PostBack. ChildrenAsTriggers is true, so children cause it to update.
theDropDownList's AutoPostBack is true, so it will postback on change. EnableViewState is true (false makes it not even load). SelectedIndexChange links to the right function, and I know that it's getting called by putting a break inside it during debug mode.
Here is the SelectedIndexChanged method:
public void theDropDownList_OnSelectedIndexChanged(object sender, EventArgs e)
{
//get value that is stored in theLabel - I know this value is correct every time
int theValueFromTheLabel = Int32.Parse(theLabel.Text);
//populate theGridView with data from the DB
theGridView_Populate(theValueFromTheLabel);
//update theUpdatePanel (it works for the first change whether this line is here or not)
theUpdatePanel.Update();
}
I've tried both with and without the updatepanel.Update(); method, and it's the same result: the first change of theDropDownList's value works, and every following change does nothing.
The function to actually populate the GridView is pretty simple:
protected void theGridView_Populate(int theValueFromTheLabel)
{
//get value from theDropDownList - this value does change when theDropDownList's value changes
int theValueFromTheDropDownList = Int32.Parse(theDropDownList.SelectedValue);
//get data from DB - the data here does change every time theDropDownList's value changed
ComplexClassController controller = new ComplexClassController();
List<ComplexClass> data = controller.GetData(theValueFromTheLabel, theValueFromTheDropDownList);
//load theGridView - this changes the data, but doesn't refresh theGridView to be able to see it
theGridView.DataSource = data;
theGridView.DataBind();
}
Any ideas? I must be misunderstanding the events behind UpdatePanel.

what is valueLabel? It doesn't look like it ever gets changed?
Why not just do ((DropDownList)sender).selectedValue to get your value to redatabind the gridview with?
Kev

It does not seems to be any problem of getting value from dropdown list the reason might be in your giving data source of your combo
place load of combo in !postback of page load event some thing like this
protected void Page_Load(object sender, EventArgs e)
{
if(!ispostback){
Loadcomobo();
}
}
if its not the case so can you place your page load event code here
thanks...

I'm still not sure why it updated once and then never again, but the problem has been fixed by placing the DropDownList and the GridView in their own UpdatePanels instead of the same one.

Try adding a trigger to the update panel
<triggers>
<asyncpostback ControlID="theDropDownList" />
</triggers>
Or something like that before the
</asp:UpdatePanel>

Dynamically adding a command button to a GridView

I'm having an issue with trying to add a button to my grid. My GridView is first loaded with data in the PageLoad event.
I'm then taking the data in the first cell of each row, and creating a button that will link to a URL. To get the URL, I have to run a query with the data in the first cell as a parameter. I was doing this in the RowDataBound event at first, but hitting that query for every row was making it really slow.
So I decided to add a button that would retrieve the URL only when you clicked the button.
Here's my GridView:
<asp:GridView ID="gvResults" runat="server"
OnRowDataBound="gvResults_RowDataBound"
OnRowCommand="gvResults_RowCommand">
</asp:GridView>
And my code:
protected void gvResults_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.DataItem != null)
{
LinkButton lb = new LinkButton();
lb.CommandArgument = e.Row.Cells[0].Text;
lb.CommandName = "NumClick";
lb.Text = e.Row.Cells[0].Text;
e.Row.Cells[0].Controls.Add((Control)lb);
}
}
protected void gvResults_RowCommand(object sender, CommandEventArgs e)
{
switch (e.CommandName.ToLower())
{
case "numclick":
string url = GetUrl(e.CommandArgument.ToString());
Response.Redirect(url);
break;
default:
break;
}
}
The grid generates fine, the button gets added to the grid for each row. But when I click on it, the RowCommand event doesn't fire, and the page just refreshes.
Does anyone know what the issue is?

Why use a dynamic button at all? You can easily put the linkbutton directly into the markup of the gridview (as long as you don't mind using a template field) and there will be no need to mess around with the RowDataBound event.
Your markup would look something like the following:
<Columns>
<asp:TemplateField HeaderText="SomeHeaderText">
<ItemTemplate>
<asp:LinkButton ID="lnkBtn" runat="server" CommandName="NumClick" CommandArgument= '<%# (string)Eval("dbValue") %>' Text='<%# (string)Eval("dbValue") %>'></asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField></asp:BoundField>
<asp:BoundField></asp:BoundField>
<asp:BoundField></asp:BoundField>
</Columns>
Add breakpoints to the RowCommand event and make sure that you can hit the breakpoints.
The problem may lie elsewhere.
Also, make sure that you're not databinding on postback.

You have a big trouble with your code. It's pretty hard for me to explain what's your big mistake, but I can easily tell you how to fix.
The problem is that you generate a new button inside the RowDataBound event, definitely the wrongest choice. The button gets rendered because it exists after that event when page renders, but doesn't exist before data binding. If you bind data everytime you load the page (even during postback) the button still gets rendered because you generate a new button.
But since the button doesn't exist before data binding, it cannot raise events. You must declare the button from markup into a template of GridView, then access it not by using new LinkButton() but by using e.Row.Cells[0].FindControl("buttonId") and set its text. Then, you have to set its markup in order to fire its own Command event (not RowCommand) and handle it as you used (don't forget to set CommandArgument during data binding)
[Edit] I also made a mistake: controls inside data bound controls also don't exist before data binding. But they are initialized not with new Control() (by the private methods of data bound control) but with Page.LoadControl(typeof(Control)). That's the first thing you must fix when you load controls dynamically!!

Because the control is added dynamically on databind and you have to databind the gridview for each postback, the control being "clicked" is different each time. The event doesn't fire because at the time it needs to fire it doesn't exist as it did in the last iteration of the page.
I notice you don't have any logic determine if the button should be there, and it always goes into cell[0].
You should place this button into a TemplateItem so that it exists properly. If you have a need to do it in code-behind, you are probably better served doing it in the RowCreated event.