I have a series of controls (3 labels, 3 text boxes, and 2 buttons) that are created when the user clicks a button on my page. The page does its postback with the commands that will generate these controls. However, when I fill in my textboxes and click one of the newly generated buttons (btnCreate), nothing happens, and the page just reloads once again.
What I want to happen is that when the user clicks btnCreate, it fires its function, and puts the TextBox.Text into a database. But again, when btnCreate is clicked, nothing happens.
Here is the code for the generated buttons (It's the same function that generates the text boxes, which I've excluded here):
Protected Sub createSpecialNotes()
Dim btnCreate As Button = New Button
Dim btnClear As Button = New Button
'Place properties
lblSubject.Text = "subject"
lblSubject.ID = "lblSubject"
lblSubject.Width = 700
lblAgenda.Text = "Agenda Note"
lblAgenda.ID = "lblAgenda"
lblAgenda.Width = 700
lblMinutes.Text = "Minutes Note"
lblMinutes.ID = "lblMinutes"
lblMinutes.Width = 700
btnCreate.Text = "Create"
btnCreate.ID = "btnCreate"
btnClear.Text = "Clear"
btnClear.ID = "btnClear"
'Add handlers for buttons
AddHandler btnCreate.Click, AddressOf btnCreate_Click
AddHandler btnClear.Click, AddressOf btnClear_Click
plhCreateSpecialNotes.Controls.Add(btnCreate)
plhCreateSpecialNotes.Controls.Add(btnClear)
End Sub
And for the sake of simplicity, let's just say btnCreate needs only to display the textboxes' contents.
Edit1: The call for create special notes is on page_preInit. It's call consists of the following
Protected Sub Page_PreInit(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreInit
'Find the control that was fired
Dim controlFired As Control = GetPostBackControl(Me.Page)
If (controlFired IsNot Nothing) Then
If (controlFired.ClientID.ToString() = "btnCreateSpecial") Then
Call createSpecialNotes()
End If
If (controlFired.ClientID.ToString() = "btnCreate") Then
'i've tried putting things here to no avail.
End If
End If
End Sub
The function getpostbackcontrol looks like this
Public Shared Function GetPostBackControl(ByVal thePage As Page) As Control
Dim myControl As Control = Nothing
Dim ctrlName As String = thePage.Request.Params.Get("__EVENTTARGET")
If ((ctrlName IsNot Nothing) And (ctrlName <> String.Empty)) Then
myControl = thePage.FindControl(ctrlName)
Else
For Each Item As String In thePage.Request.Form
Dim c As Control = thePage.FindControl(Item)
If (TypeOf (c) Is System.Web.UI.WebControls.Button) Then
myControl = c
End If
Next
End If
Return myControl
End Function
I hope this helps to clear things up as to why I'm having trouble.
What would be really useful here is to know when you're calling createSpecialNotes(). But most probably what you are missing is the life-cycle of the page.
Make sure createSpecialNotes() is called OnInit of your page. Anything after that is too late and your event handler won't be fired.
If OnLoad of your page is reached and you haven't yet bound the handler to your control, then it won't be fired.
I recommend that you read this article carefully. http://msdn.microsoft.com/en-us/library/ms178472.aspx
Related
I create a readonly textbox dynamically on page load/init and on the first load (not IsPostBack) I set the text. I also have a button on the page with a click event that changes the content of the textbox. Using another button, I read the text of the textbox. The problem is as follows:
If I click the button that changes the textbox and then click the button that reads the text of the textbox, it gets it fine.
If I just load the page and click the button that reads the text of the textbox, it brings back an empty string
I need both scenarios to bring back a result - whether it's the original text or the new programmatically changed text.
Example code:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim Textbox As New TextBox()
Textbox.ID = "Bob"
Textbox.ReadOnly = True
If Not IsPostBack Then
Textbox.Text = "Initial Text"
End If
Content.Controls.Add(Textbox)
Dim Button As New Button()
Button.Text = "Change text"
AddHandler Button.Click, AddressOf Button_Click
Content.Controls.Add(Button)
End Sub
Protected Sub Button_Click(ByVal sender As Object, ByVal e As EventArgs)
'FindControlRecursive is locally defined - just finds a control based on root control and ID
CType(FindControlRecursive(Content, "Bob"), TextBox).Text = "Hmmmmm"
End Sub
Private Sub Submit_Click(sender As Object, e As EventArgs) Handles Submit.Click
Dim Textbox As TextBox = CType(FindControlRecursive(Content, "Bob"), TextBox)
MsgBox(Textbox.Text)
End Sub
I could just reinitialise the textbox each time but this is just an example and in practice I'll be pulling it from SQL and if I have several read only controls on the page I'd rather get the control to persist its text rather than going back to SQL each time.
I found two ways to solve this, the second being the more favoured approach (depending on situation):
Specifically add the initial text to the viewstate and then set the text on each postback using the value from viewstate:
If Not IsPostBack Then
Textbox.Text = "Initial Text"
ViewState("Bob") = Textbox.Text
Else
Textbox.Text = ViewState("Bob")
End If
Add a PreRender event to the textbox that just sets it text to itself. This takes place after the ViewState starts being tracked so it's added to the viewstate via the control and is persisted across postbacks:
If Not IsPostBack Then
Textbox.Text = "Initial Text"
AddHandler Textbox.PreRender, AddressOf PersistPastInitialLoad
End If
And add new sub:
Protected Sub PersistPastInitialLoad(ByVal sender As Object, ByVal e As EventArgs)
'This is just for example - would need refining for different types of controls
CType(sender, TextBox).Text = CType(sender, TextBox).Text
End Sub
Essentially they both do the same thing - hold the text in viewstate - but it depends on implementation which is the best to use. The first implementation might be a bit easier to read/work with but it would result in redundant viewstate bloat if you click the button to change the textbox text (i.e. you'll have the initial text in viewstate against the viewstate key you created as well as the current text added to viewstate by the control onchange).
I have some code that handles a timer method, that just updates a label and changes it to a last updated at this time.
Protected Sub specialNotesTimer_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles specialNotesTimer.Tick
Label1.Text = "Panel refreshed at: " + DateTime.Now.ToLongTimeString()
End Sub
When it ticks however, any other control on the page cannot be found via a button press. Image buttons or my other dynamically created controls, w.e the case, are missing.
I have a function that finds the fired control on the page, then returns the control so I can determine what to do
Public Shared Function GetPostBackControl(ByVal thePage As Page) As Control
Dim myControl As Control = Nothing
Dim ctrlName As String = thePage.Request.Params.Get("__EVENTTARGET")
If ((ctrlName IsNot Nothing) And (ctrlName <> String.Empty)) Then
myControl = thePage.FindControl(ctrlName)
Else
For Each Item As String In thePage.Request.Form
Dim c As Control = thePage.FindControl(Item)
If (TypeOf (c) Is System.Web.UI.WebControls.Button) Then
myControl = c
End If
Next
End If
Return myControl
End Function
This works before the timer.tick, but not after. The control won't be listed as an Item in thePage.Request.Form, and it'll throw a null exception, when I know the control is there.
The problem im having is a little complicated to explain, so please bear with me. I have 2 button controls. In the page load, I wanted to know what button created a postback on the page load. Through research I have found this snippet below and it works as expected. So here is my scenario of events that occur when click on the button.
1. Click the button does a postback
2. Runs the function below and tell me the id of the button
3. Runs the clicked event handlers for that button
Protected Sub btnCalc_Click(ByVal sender As Object, ByVal e As EventArgs) Handles btnCalc.Click
' Do this
End Sub
The problem comes in when I click the second button, it does steps 1 and 2 but NEVER DOES 3. Through testing, I have that it only does 1, 2, and 3 on the first button clicked. I have no clue why this is happening?
Function GetPostBackControlName() As String
Dim control As Control = Nothing
Dim ctrlname As String = Page.Request.Params("__EVENTTARGET")
If ctrlname <> Nothing AndAlso ctrlname <> [String].Empty Then
control = Page.FindControl(ctrlname)
Else
Dim ctrlStr As String = [String].Empty
Dim c As Control = Nothing
For Each ctl As String In Page.Request.Form
c = Page.FindControl(ctl)
If TypeOf c Is System.Web.UI.WebControls.Button Then
control = c
Exit For
End If
Next
End If
Try
Return control.ID.ToString
Catch
Return ""
End Try
End Function
You really should look into just assigning Click event handlers to your buttons. Asp.net was designed purposely so that you wouldn't have to parse through the request object like you are doing above.
The problem im having is a little complicated to explain, so please bear with me. I have 2 button controls. In the page load, I wanted to know what button created a postback on the page load. Through research I have found this snippet below and it works as expected. So here is my scenario of events that occur when click on the button.
1. Click the button does a postback
2. Runs the function below and tell me the id of the button
3. Runs the clicked event handlers for that button
Protected Sub btnCalc_Click(ByVal sender As Object, ByVal e As EventArgs) Handles btnCalc.Click
' Do this
End Sub
The problem comes in when I click the second button, it does steps 1 and 2 but NEVER DOES 3. Through testing, I have that it only does 1, 2, and 3 on the first button clicked. I have no clue why this is happening?
Function GetPostBackControlName() As String
Dim control As Control = Nothing
Dim ctrlname As String = Page.Request.Params("__EVENTTARGET")
If ctrlname <> Nothing AndAlso ctrlname <> [String].Empty Then
control = Page.FindControl(ctrlname)
Else
Dim ctrlStr As String = [String].Empty
Dim c As Control = Nothing
For Each ctl As String In Page.Request.Form
c = Page.FindControl(ctl)
If TypeOf c Is System.Web.UI.WebControls.Button Then
control = c
Exit For
End If
Next
End If
Try
Return control.ID.ToString
Catch
Return ""
End Try
End Function
I am building a wizard in asp.net. I have an main aspx page which will have NEXT and PREVIOUS button for Navigation. On click of each NEXT or PREVIOUS appropriate user control will be loaded.
In one user control I have to create dynamic checkboxes as shown below:
Public Class ucQuestion
Inherits System.Web.UI.UserControl
#Region "UserControl Events"
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Try
If Not (Page.IsPostBack) Then
AddControls(0)
End If
Catch ex As Exception
Throw ex
End Try
End Sub
#End Region
Protected Friend Sub AddControls(ByVal iListQuestionCount As Integer)
Try
Dim oExam As New BusinessObject.Wizard.ExamVM
If (System.Web.HttpContext.Current.Session(BusinessLayer.Constants.WizardObjectCollection) IsNot Nothing) Then
oExam = DirectCast(System.Web.HttpContext.Current.Session(BusinessLayer.Constants.WizardObjectCollection), BusinessObject.ExamWizard.ExamVM)
End If
'divQuestion.Controls.Clear()
Dim ctrl As New Literal
ctrl.ID = "lit" + iListQuestionCount.ToString()
ctrl.Text = oExam.Wizard.ExamQuestions(iListQuestionCount).Label
divQuestion.Controls.Add(ctrl)
For iLoopChildCount As Integer = 0 To oExam.Wizard.ExamQuestions(iListQuestionCount).Choices.Count - 1
Dim childctrl As New CheckBox
'childctrl.AutoPostBack = True
childctrl.ID = "chk" + (iLoopChildCount + 1).ToString()
childctrl.Text = oExam.Wizard.ExamQuestions(iListQuestionCount).Choices(iLoopChildCount).Label
childctrl.Checked = oExam.Wizard.ExamQuestions(iListQuestionCount).Choices(iLoopChildCount).IsSelected
'AddHandler childctrl.CheckedChanged, AddressOf OnCheckedClick
divQuestion.Controls.Add(childctrl)
Next
Catch ex As Exception
Throw ex
End Try
End Sub
NoW the problem is in my Main.aspx page if user has selected any checkbox in usercontrol I want to save the value in session on NEXT button Navigation click event.
I tried following code in NEXT Button Click but it was unsucessfull.
For iLoopChildCount As Integer = 0 To oExamQuestions(ListIndex).Choices.Count - 1
Dim ctrl As Control
If (ucQuestion1.FindControl("chk" + (iLoopChildCount + 1).ToString()) IsNot Nothing) Then
ctrl = DirectCast(ucQuestion1.FindControl("chk" + (iLoopChildCount + 1).ToString()), CheckBox)
If (DirectCast(ctrl, CheckBox).Checked) Then
oBallotQuestions(ListIndex).Choices(iLoopChildCount).IsSelected = True
End If
End If
Next
That's the hard way.
Here is the easy way.
Define an interface and implement it in the User Control that represents this action. This might be GetNamesOfSelectedValues or whatever is appropriate. (Technically an interface isn't required, but I find it good practice and it makes for "more well defined contracts" in many cases.)
Use the interface defined on said Child in the Parent page code. Use this only after the OnLoad of the Child Control (which happens after the page load event) or the controls will not be restored yet.
That is, the parent should not know about any controls in the custom User Control.
This approach works well.