With a custom control (lets call it TwoLists) that contains two asp:DropDownList (defined in .ascx), I create an instance of TwoLists in my unit test, to find its child lists are nothing.
Public Sub test_TwoLists()
Dim instance As TwoLists = New TwoLists()
Dim list1 As DropDownList = instance.FindControl("list1")
Dim list2 As DropDownList = instance.FindControl("list2")
Assert.IsNotNull(list1)
Assert.IsNotNull(list2)
End Sub
Why is the control not initialized with it's child controls?
Note: This control is created/intialised and works fine when being used in an .aspx and I navigate to the page.
Related
currently I am working on a project named online exam.
All the controls are dynamically created.
I have a webpage where I want to display the student details.
I displayed those details correctly in a table.
Now here comes the time to edit those details.
To edit a record I use the linked button named edit.
When a user clicks on that Linked button the data in that row is replaced with new textboxes.
Upto here I am OK.
Now when I click on the save changes button after making changes to the textboxes.
The old values are not replaced by the new values and the old values remains.
The code for creating textboxes in the table is as follows :
Public Sub Edit_Click(ByVal sender As Object, ByVal e As System.EventArgs)
For x As Integer = 0 To EditList.Count - 1
If sender.id.substring(4) = EditList(x).ID.Substring(4) Then
Session("PreviousRollNo") = RollNoList(x).Text
Dim txtName As New TextBox
txtName.Text = NameList(x).Text
NameList(x).Text = ""
NameList(x).Parent.Controls.Add(txtName)
txtList.Add(txtName)
Dim txtCourse As New TextBox
txtCourse.Text = CourseList(x).Text
CourseList(x).Text = ""
CourseList(x).Parent.Controls.Add(txtCourse)
txtList.Add(txtCourse)
Dim txtAdmissionDate As New TextBox
txtAdmissionDate.Text = AdmissionList(x).Text
AdmissionList(x).Text = ""
AdmissionList(x).Parent.Controls.Add(txtAdmissionDate)
txtList.Add(txtAdmissionDate)
Dim btnSaveChanges As New Button
btnSaveChanges.Text = "Save Changes"
EditList(x).Text = ""
EditList(x).Parent.Controls.Add(btnSaveChanges)
AddHandler btnSaveChanges.Click, AddressOf btnSaveChanges_Click
Session("EditButtonClicked") = True
Dim btnCancel As New Button
btnCancel.Text = "Cancel"
DeleteList(x).Text = ""
DeleteList(x).Parent.Controls.Add(btnCancel)
AddHandler btnCancel.Click, AddressOf btnCancel_Click
Session("CancelButtonClicked") = True
txtName.Focus()
Exit For
End If
Next
End Sub
The code for Save Changes button is as follows :
Public Sub btnSaveChanges_Click(ByVal sender As Object, ByVal e As System.EventArgs)
If txtList(0).Text = "" Then
Dim trError As TableRow = New TableRow
Dim tdError As TableCell = New TableCell
tdError.ColumnSpan = 7
Dim lblError As New Label
lblError.Text = "Please enter name of the student."
lblError.ForeColor = Drawing.Color.Red
tdError.Controls.Add(lblError)
trError.Controls.Add(tdError)
tbl.Controls.Add(trError)
ElseIf txtList(1).Text = "" Then
Dim trError As TableRow = New TableRow
Dim tdError As TableCell = New TableCell
tdError.ColumnSpan = 7
Dim lblError As New Label
lblError.Text = "Please enter the course."
lblError.ForeColor = Drawing.Color.Red
tdError.Controls.Add(lblError)
trError.Controls.Add(tdError)
tbl.Controls.Add(trError)
ElseIf txtList(2).Text = "" Then
Dim trError As TableRow = New TableRow
Dim tdError As TableCell = New TableCell
tdError.ColumnSpan = 7
Dim lblError As New Label
lblError.Text = "Please enter the Admission Date"
lblError.ForeColor = Drawing.Color.Red
tdError.Controls.Add(lblError)
trError.Controls.Add(tdError)
tbl.Controls.Add(trError)
Else
Dim cb As New OleDbCommandBuilder(da)
Dim editRow() As DataRow
editRow = ds.Tables("Student_Detail").Select("Roll_No = '" & Session("PreviousRollNo") & "'")
editRow(0)("Name") = txtList(0).Text
editRow(0)("Course") = txtList(1).Text
editRow(0)("Admission_Date") = txtList(2).Text
da.Update(ds, "Student_Detail")
Page.Response.Redirect("ChangeUserDetails.aspx")
End If
End Sub
I get the error sying that array is out of the bounds. on the first line of the btnSaveChanges_Click.
It means txtlist is always cleared when I click on Save Changes Button.
So I stored txtList in a Session like Session("txtList") = txtList.
and retrieved the data from that. But now I get the old values of the textbox instead of the newer ones.
Here txtList is a list (of Textbox)
Firstly, welcome to the ASP.NET WebForms Page Life Cycle. Remember its pattern with the simple mnemonic: SILVER = Start, Init, Load, Validate, Events, Render.
Secondly, HTTP is stateless. WebForms does an amazing job of hiding this fact from you using ViewState until you do something a little out of the ordinary (as you're now attempting), and it all appears to fall apart. What's really happening is that you're starting to see side-effects of how WebForms is managed, and how it's not as much like WinForms (or another stateful system) as you might think.
When you're responding to an event server-side in WebForms, it's easy to get the impression that nothing has changed. That the entire page is as you left it "last time". All the controls are there, the values you may have set programatically are still set. Magic. Not magic. What's actually happened is the entire page has been re-constructed to respond to that event. How was it re-constructed? By a combination of your page definition (markup), actions taken in control event handlers, and the form data posted back by the client.
Confusing? OK, let's consider an example. Say you've got a page with two controls on it. A textbox named txtInput and a button named btnSubmit with event handler btnSubmit_Click. When the user first requests the page, the HTML for these controls is derived from your markup (aspx page) and returned to the client. Next, the user sets a value in txtInput and clicks the submit button. The server then re-creates the page from scratch based on your markup. At this early stage of the life-cycle, the controls still have their default values. We then hit the Load stage of the life-cycle, and "if the current request is a postback, control properties are loaded with information recovered from view state and control state." In other words, by the time the life-cycle gets to Init, the control has been created from markup, but still has its default value. The Load stage then sets the value according to Postback data.
Left wondering how this applies to your scenario? You're adding your dynamic controls in response to a control event. There's two things wrong with that:
It's too late in the page life-cycle for Init to set the values based on data posted back from the client (recall SILVER, Event is after Init).
Your button click event handler is only run once, in response to the postback where the user clicked the button. But remember on each postback the page is entirely re-created. So the dynamic controls no longer exist as far as the server is concerned! You'll notice that not only are the controls not present server side when responding to the submit event, but after the page has handled it, they're no longer present client-side either.
So what's the answer? Well the "Life-Cycle Events" section of the page I linked offers a clue. It states that the PreInit event be used to (among other things) "Create or re-create dynamic controls". Why would we do it in PreInit? So it's early enough in the page life-cycle for the later events to properly handle it (like setting the values posted back from the client).
Now, I know, you want to add the controls based on the user clicking on the button. How does that fit? The trick is that you've got to manage the "state" yourself. Huh? the state? By this I mean MyDynamicControlsShouldBeShown = true / false. When the button is clicked, creating the controls in response to the button-click event handler is the right action (there's not really any choice there). But you need to store that state somehow so you know on subsequent requests to the page, whether those controls should be re-created in PreInit. One neat option would be to check for the ID of your dynamic control in Request.Form.Keys. If the control ID is present in the Keys collection, then the user is posting back a value for the control, so you should re-create it.
A side-note on the use of Session
Hopefully based on the above you've realised why putting the controls into Session didn't work. But to be clear, the controls you put into the Session object were no longer part of a page that existed (remember, the page gets completely re-created for each request. Those controls were no longer hooked up to the Page events, so didn't get their values populated between Page Init and Load. If somehow it did work, it still wouldn't be a particularly good idea, as Session is not per-request. So what would happen if a user had the same page open in multiple tabs? Strange things, that's what.
On my webpage I am loading multiple instances of a usercontrol, sometimes the usercontrol is laoded within itself. I need to save a bunch of properties for the round trip of a post back but i am confused on how to save those properties to ViewState and set them again to the repeater items within the usercontrol.
Can anyone help me in this situation, I have read the MSDN on Viewstate but I am not understanding it quite well for some reason
This is how I load the parent user controls (child controls are loaded the same way with the same user control)
Protected Sub Load_Controls(ByVal list As List(Of BSEvaluationGroup.category), ByVal gid As Integer, ByVal pid As Integer, ByVal fid As Integer)
Dim item As BSEvaluationGroup.category
For Each item In list
Dim ctl As PerformanceEvaluationSubcontractorControl = CType(Page.LoadControl("PerformanceEvaluationSubcontractorControl.ascx"), PerformanceEvaluationSubcontractorControl)
ctl.categoryid = item.catid
ctl.categoryname = item.catname
ctl.projectid = pid
ctl.folderid = fid
ctl.groupid = gid
ctl.parentid = item.parid
ctl.clist = item.categories
ctl.plist = item.points
ctl.parentpage = Me
ctl.EnableViewState = "true"
If (Not subcon Is Nothing AndAlso Not subcon.points Is Nothing) Then
ctl.epnts = subcon.points
End If
AddHandler ctl.BubbleCalculate, AddressOf Me.PostRating
Select Case gid
Case 1
Me.officephld.Controls.Add(ctl)
Dim ohrule As HtmlGenericControl = New HtmlGenericControl("hr")
ohrule.Style.Add("width", "100%")
ohrule.Style.Add("background-color", "Silver")
ohrule.Style.Add("size", "1px")
ohrule.Style.Add("border-width", "0")
ohrule.Style.Add("padding-top", "1px")
ohrule.Style.Add("float", "left")
Me.officephld.Controls.Add(ohrule)
Case 2
Me.sitephld.Controls.Add(ctl)
Dim shrule As HtmlGenericControl = New HtmlGenericControl("hr")
shrule.Style.Add("width", "100%")
shrule.Style.Add("background-color", "Silver")
shrule.Style.Add("size", "1px")
shrule.Style.Add("border-width", "0")
shrule.Style.Add("padding-top", "1px")
shrule.Style.Add("float", "left")
Me.sitephld.Controls.Add(shrule)
End Select
Next
End Sub
Accessing view-state is simple such as ViewState("PropertyName"). The View State bag is specific to a control instance so you can use same property name within multiple control types and instances.
Only important thing here is that ASp.NET run-time has to match view-state bags to control instances and for that it uses ID property (which is unique within the parent naming container). So its important that you assign unique IDs to your dynamic user control instances ( and maintain same control tree hierarchy and ids on postback - essentially it means that execute the same code on postback and don't use random ids). So your code should be something like
...
Dim n As Integer
n = 1
For Each item In list
Dim ctl As PerformanceEvaluationSubcontractorControl = CType(Page.LoadControl("PerformanceEvaluationSubcontractorControl.ascx"), PerformanceEvaluationSubcontractorControl)
ctl.ID = "MyCtl" & n.ToString()
ctl.categoryid = item.catid
....
It was a control ID issue, I removed it instead of adding an ID
There are test.aspx page and test.ascx web user control.
I have a button in test.aspx = btn_test and above code in my button is :
Dim ct As Control = Page.LoadControl("test.ascx")
Panel1.Controls.Add(ct)
There is a dropdownlist with value 1 to 10 in test.aspx and there is label_test in test.ascx
I need some code when test.ascx loading, get dropdownlist.selectedvalue and show it in label_test.
Please help me !
There are a number of ways to implement this. One you could try would be to cast the test.ascx web control being loaded like so (replace TestControl with the class name for the control):
Dim ct As TestControl = CType(Page.LoadControl("test.ascx"), TestControl)
And then create a public property in the control which you would use to set the value from the DropDownList.
Dim ct As TestControl = CType(Page.LoadControl("test.ascx"), TestControl)
ct.DropDownListValue = DropDownList.SelectedItem.Value
Panel1.Controls.Add(ct)
This property would then be used to set the labels value (either directly using the set accessor or via a method within the test.ascx control).
I am trying to create a more detailed item template for the standard CheckBoxList control. It exposes an ITemplate property called TemplateControl but I wasn't able to find a straightforward resource on how to actually use it. Here's the code I have so far:
Protected Overrides Sub OnLoad(ByVal e As System.EventArgs)
MyBase.OnLoad(e)
Dim items As New List(Of ListItem)
items.Add(New ListItem() With {.Text = "A", .Value = "1"})
items.Add(New ListItem() With {.Text = "B", .Value = "2"})
items.Add(New ListItem() With {.Text = "C", .Value = "3"})
Dim lst As New CheckBoxList()
Dim tpl As ITemplate = LoadTemplate("~/CustomListItem.ascx")
Dim g As New TemplateControlWrapper()
tpl.InstantiateIn(g)
lst.TemplateControl = g
lst.DataSource = items
lst.DataBind()
Form.Controls.Add(lst)
End Sub
Class TemplateControlWrapper
Inherits UserControl
End Class
It seems to be ignoring the TemplateControl property completely. Any ideas?
CheckBoxList's TemplateControl property does not actually allow you to modify the template of the CheckBoxList. This is a property inherited all the way from System.Web.UI.Control, and it means the templated control that the CheckBoxList lives in, or put another way, the .aspx page, .ascx user control, or master page that the control lives on. (If the control is included as part of a composite control, I honestly don't know without experimenting if the TemplateControl property would return null, or keep going up the control chain until it found a Page or UserControl.)
The CheckBoxList control does not offer the kind of template modification you are looking to do. You may need to custom-bind a Repeater or DataList (with a CheckBox control in the ItemTemplate) in order to achieve the functionality you're looking for.
You are missing a couple things... this MSDN page has a pretty straightforward example:
http://msdn.microsoft.com/en-us/library/36574bf6.aspx
For starters, you are missing INamingContainer.
I have an aspx page with three web controls: one to control the List Users page, one to control the Edit Users page, and one to control the Add User page. I have discovered a method for accessing these elements, but it seems to be limited. Here is what I have done:
Protected Sub editUser(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewEditEventArgs)
'set selected user from gridview.
Dim index As Integer = e.NewEditIndex
Dim userId As Integer = gvListUsers.DataKeys(index).Value
Session.Item("SelectedUserId") = userId
'show edit page, hide list and add page.
With Page.Form.Controls(1)
.Controls(getControlId("loadAddUser")).Visible = False
.Controls(getControlId("loadEditUser")).Visible = True
.Controls(getControlId("loadListUser")).Visible = False
End With
End Sub
The getControlId function looks like this:
Public Function getControlId(ByVal control As String) As Integer
Dim enumer As System.Collections.IEnumerator = Page.Form.Controls.Item(1).Controls.GetEnumerator
Dim i As Integer
For i = 0 To (Page.Form.Controls.Item(1).Controls.Count - 1)
If Page.Form.Controls(1).Controls.Item(i).ID = control Then
Return i
End If
Next
Return Nothing
End Function
This works in most cases. However, I am unable to access the "enabled" attribute of these web controls. Why is this, and how might I access that attribute?
Thanks :)
You could raise events from your UserControls which you subscribe to in the parent ASPX page. In the parent page event action you could enable/disable your controls,
Here's an example of events in UserControls: http://codebetter.com/blogs/brendan.tompkins/archive/2004/10/06/Easily-Raise-Events-From-ASP.NET-ASCX-User-Controls.aspx
Something else to think about: are you getting any benefit from moving this code into usercontrols? Would any of the individual controls be re-usable on their own? Creating tightly coupled controls that rely on each other being present doesn't give you much re-usability of the individual controls.
Visible is a property provided by the System.Web.UI.Control class, which is why you can access it directly. Enabled is not a property on this class, so you need to map the control object to a variable of the type of your custom control class if you want to access the Enabled property.
Dim myControl As TheAddUserControl
With Page.Form.Controls(1)
myControl = .Controls(getControlId("loadAddUser"))
myControl.Enabled = False
.Controls(getControlId("loadEditUser")).Visible = True
.Controls(getControlId("loadListUser")).Visible = False
End With
To expose an Enabled property in you user control:
Public Property Enabled As Boolean
Get
Return (Child1.Enabled And Child2.Enabled And Child3.Enabled)
End Get
Set(ByVal value As Boolean)
Child1.Enabled = value
Child2.Enabled = value
Child3.Enabled = value
End Set
End Poperty