Web Forms :: User Controls Are Null When Referenced Inside The Code Behind For The User Control?
Sep 1, 2010
I have an ASP.NET 4.0 application with some simple user controls. The user controls work fine on the design surface (VS.NET 2010), but when they're loaded during application execution, nothing shows up.
Futhermore, the various child controls of the user controls are null when referenced inside the code behind for the user control.
The code behind for the user control executes as expected, but any reference to child controls are null.
It's like ASP.NET is never parsing the ASCX to create the instances of the child controls.
I don't think I understand fully how ASP.NET does inheritance of controls.I have a user control, ucBase, which has an asp.net label in the ascx file. Code behind references the label and it works fine during run time if the control is not a parent for another user parent.
If I have another user control, ucChild, inheriting from ucBase, the label in ucBase's code is always null. ucChild has no controls in its ascx fileThe server controls (like the label) needs to be declared in the ascx file and not created programmatically.What needs to be done for ucBase to see its own controls when it's a parent user control?
I have a web user control that represents a simple message box. It is used to display simple messages like "Item has been deleted", or "The item was saved successfully".
On the other hand, I have another web user control that represents the item in the form of an editable form (I made this a user control because this is used in two different pages). I want to embed an instance of the message box user control inside the editable form. I am writing this right after the @Control directive:
Instead of using @Register directives, I register the user controls in web.config and so far this has worked just fine.
With the above markup, the project compiles, but whenever I try to navigate to a page that contains this construct, I get an HttpParseException exception. Furthermore, Visual Studio states that the tack w7rc9:MessageBox doesn't represent a known control.
I have a ObjectDataSource and a ListView referencing it.
I have created a Templated User Control (see: http://msdn.microsoft.com/en-us/library/36574bf6.aspx) and placed it in the ListView's InsertItemTemplate It has one template <ContentTemplate>. Inside that template, I've defined a couple of server controls with their properties = '<%# Bind("colName") #>'.
I'm working on a user control that renders couple nested divs (a rounded corner box to be frank). This is a templated user control, which means that user can put any control he wants into the header, body or footer of this box. Everything is working fine, except the fact that server-side controls can't be retrived from my box. Take a look at this code:
Now codebehind of that control:
I have cut out all the unimportant stuff.Now when I use this control:
I want to access controls in page codebehind file (on Page Load): LiteralNewses.Text=""; but compiler returns an error that LiteralNewses doesn't exist. Also FindControl method can't find this literal.Any tips on what's wrong with this code? According to MSDN, setting TemplateInstance to Single ensures that controls from template will be accessible but not in my case...
i have a base user control (WC1) which inherits from WebUserControl and a child user control (WC2) which inherits from WC1. I added a textBox and a label to WC1 in vs design view not code behind. But all the server controls that i put in WC1 are null and give null pointer exception.I tried to access textBox and label in different events but the all of them are null.
Steps to reproduce the error:
create a web user control called WC1 by add a new item in VS added a textBox and label server control to WC1 in design view of VS and put code behind: var value = txetBox.Text; created another web user control called WC2 by add a new item in VS and change its base class to WC1 in its code behind create a web page by adding a new item in vs and drag WC2 to the design view of the page run the page then you will see the exception for the codebehind in WC1
<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="WC2.ascx.cs" Inherits="WebApplication1.WC2" %>
can web server controls of WC1 be instantiated in this case? or can user control inherit from another user control and web server controls of parent user control be carried to its children without worring the layout?
I have a user control called ucTriStateButton. It raises an event when it is clicked, called TriStateButtonClicked. If I put this user control on a page, it works fine. Here is the declaration on the .aspx page:
When the button is clicked the method tsbTest_TriStateButtonClicked executes correctly.
The problem is when I put the user control in template field of a GridView.
There is no way to hook the event handler to the control in Page_Load because I cannot get a reference to tsbMorning. So I did it in the RowDataBound event handler of the GridView, where I also do a bunch of other row-specific stuff. Although this builds and runs, the event is never actually subscribed to and so never gets fired.
So the question is - how can I handle an event from many instances of the same user control within a GridView? I am calling the same bit of code regardless of which user control is actually clicked. I only need to know that one was clicked.
I am stuck into a problem, i have a user control ProductListing.ascx that contains ListView binded to an object datasource, SelectMethod and SelectCountmethod are provided as well. Everything works fine but the problem started when i add another user control declarativlly Filter.ascx in the productListing.ascx. I want to assign value to a public property MaxPrice in Filter.ascx. I am trying to set this property in the SelectMethod of ObjectDataSource. Usercontrol "Filter.ascx" throws null reference exception when i try to set its MaxPrice Property.
I tried to acced the usercontrol in Databind method of ListView , it is accessible here but viewstate is empty at this point, i saved the value in viewstate in SelectMethod of objectDatasource but i cant access viewstate in ListView Databind. Its empty. Its a simple code and no rewriting to viewstate elsewhere.
Important: My Codebehind files are in a seperate project and .ascx files in seperate project
I downloaded a sample Rolodex from here: [URL] the file to download is at the bottom of the page and it is called 'RolodexDatalist.zip (6.71 kb)' So I changed the HTML to it points to my SQL Server DB. I changed the ConnectionString to this:
Now, everything points to my DB! I thought, ok great, this should be pretty easy. However, when I debug, I get this error message: 'Null reference was unhandled by user code. Object reference not set to instance of an object. Troubleshooting Tips: use the "new" keyword to set an instance of an object.' This line is yellow:
Dim conStr As String = ConfigurationManager _ .ConnectionStrings("conStr").ConnectionString Here is the code-behind: Imports System.Data Imports System.Data.SqlClient Imports System.Collections.Generic Partial Class VB Inherits System.Web.UI.Page Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load If Not IsPostBack Then ViewState("CurrentAlphabet") = "ALL" Me.GenerateAlphabets() Me.BindDataList() End If End Sub Private Sub BindDataList() Dim conStr As String = ConfigurationManager _ .ConnectionStrings("conStr").ConnectionString Dim con As New SqlConnection(conStr) Dim cmd As New SqlCommand("spx_GetContacts") cmd.Connection = con cmd.CommandType = CommandType.StoredProcedure cmd.Parameters.AddWithValue("@Alphabet", ViewState("CurrentAlphabet")) con.Open() dlContacts.DataSource = cmd.ExecuteReader() dlContacts.DataBind() con.Close() If ViewState("CurrentAlphabet").ToString().Equals("ALL") Then lblView.Text = "all Contacts." Else lblView.Text = "Contacts whose name starts with " & _ ViewState("CurrentAlphabet").ToString() End If End Sub Private Sub GenerateAlphabets() Dim alphabets As New List(Of Alphabet)() Dim alphabet As New Alphabet() alphabet.Value = "ALL" alphabet.isNotSelected = Not alphabet.Value _ .Equals(ViewState("CurrentAlphabet")) alphabets.Add(alphabet) For i As Integer = 65 To 90 alphabet = New Alphabet() alphabet.Value = [Char].ConvertFromUtf32(i) alphabet.isNotSelected = Not alphabet.Value _ .Equals(ViewState("CurrentAlphabet")) alphabets.Add(alphabet) Next rptAlphabets.DataSource = alphabets rptAlphabets.DataBind() End Sub Protected Sub Alphabet_Click(ByVal sender As Object, ByVal e As EventArgs) Dim lnkAlphabet As LinkButton = DirectCast(sender, LinkButton) ViewState("CurrentAlphabet") = lnkAlphabet.Text Me.GenerateAlphabets() Me.BindDataList() End Sub End Class
I have made a web page in which there is login screen when user login it goes next page but my problem is if i directly enter the url of that page it open. I want it should not open unless the user log in...
i have a user control with 3 textfields (txtQuestion.text), (txtAnswr.text) and txtpts.text... i dragged 5 and drop it on my master can you help me how can i get the value of each user control's field.
I've created a multiple uploadfile user control - upload_multiple_files.ascx:
which has an update panel ID = up_upload_multiple_files this user control will be placed inside a modalpopupextender. My question is when I click in any button AddFile, RemvFile, Upload there's a postback so the page is reloaded and the modalpopupextender disapears Is there a way to to troubleshoot this?
I have create one user control of personal details, and write the geting data from database method and Load the entities in respective field,then how to bind user control in gridview and how to accecc Id of user control in aspx page.