Create dynamically LinkButton controls and EventHandlers

  • Thread starter Thread starter Kiyomi
  • Start date Start date
K

Kiyomi

Hello,



I create a Table1 dynamically at run time, and at the same time, I would
like to create LinkButton controls, also dynamically, and insert them into
each line in my Table1. I would then like that, when clicking the
LinkButton, the user can be navigated to another page, carrying a variable.
I would like to use server.transfer method instead of QueryString as I don't
want the carried variable to be visible for the user.



How can I create dynamically LinkButton controls as well as EventHandlers?



Thank you very much for your kind advice,



KK
 
Hi KK,

Okay, first you need to make sure that the form has the runat attribute set
to Server, which is the default. Then you need a placeholder, such as a DIV,
to which you can add the controls. The runat attribute of the placeholder
must also be set to Server. Then, the following code will work for you:

Protected Sub LinkButton_Click(ByVal sender As Object, ByVal e As
System.EventArgs)
Select Case CType(sender, LinkButton).ID
Case "DynamicLinkButton1"
Response.Redirect("PageName")
End Select
End Sub

Protected Sub Page_Load(ByVal sender As Object, ByVal e As
System.EventArgs) Handles Me.Load
' Instantiate LinkButton
Dim DynamicLinkButton1 As New LinkButton
' Set properties
DynamicLinkButton1.Text = "Dynamic LinkButton"
' Assign an ID you can use to filter in click event
DynamicLinkButton1.ID = "DynamicLinkButton1"
' Add event handler
AddHandler DynamicLinkButton1.Click, AddressOf LinkButton_Click

' Instantiate HTML Table
Dim Table1 As New HtmlTable
' Instantiate HTML Table Row
Dim Row1 As New HtmlTableRow
' Instantiate HTML Table Cell
Dim Cell1 As New HtmlTableCell
' Add controls to Table
Cell1.Controls.Add(DynamicLinkButton1)
Row1.Controls.Add(Cell1)
Table1.Controls.Add(Row1)

' Get place holder on Web form, in this case a DIV
Dim dynamicDIV As HtmlControl = CType(Me.FindControl("DynamicDIV"),
HtmlControl)
' Add Table1, including any controls and content
dynamicDIV.Controls.Add(Table1)
End Sub

Now, you state that you want to pass a value to the page you're redirecting
to. Since this is a new page, you can' use the viewstate, but you can add a
value to current session, using Session.Add. Then in the page that you're
redirecting to, you can access the value using Session.Item. Well, that's
one way, if you want to avoid the querystring.
 
Thank you very much, Carsten, for your advice. Could I ask you some more
questions ?



I have got "Object reference not set to an instance of an object." at the
line :



dynamicDIV.Controls.Add(Table1)



Is this because my Table1 is not really HTMLTable but is an object whose
runat attribute set to Server ? In fact, I created my table on design page
only for its title lines as I need to use column spans and row spans for the
title lines. The body of the table is generated dynamically in the code
behind.



Also, I have several LinkButtons to insert in my Table and the total number
of instances depends on the query results (can be more than hundred). How
can I define the ID for the each instance and deal with them in the
following Select Case when I have hundred IDs ?



Select Case CType(sender, LinkButton).ID
Case "DynamicLinkButton1"
Response.Redirect("PageName")
End Select



I appreciate very much your kind help,



KK
 
Kiyomi,

Inline please.

--
Carsten Thomsen
Communities - http://community.integratedsolutions.dk

Kiyomi said:
Thank you very much, Carsten, for your advice. Could I ask you some more
questions ?



I have got "Object reference not set to an instance of an object." at the
line :

dynamicDIV.Controls.Add(Table1)
Click to expand...


I assume that you don't have the static DIV element named DynamicDIV in your
Web page, which is why this line of code returns nothing:

Dim dynamicDIV As HtmlControl = CType(Me.FindControl("DynamicDIV"),
HtmlControl)
Is this because my Table1 is not really HTMLTable but is an object whose
runat attribute set to Server ? In fact, I created my table on design page
only for its title lines as I need to use column spans and row spans for
the
title lines. The body of the table is generated dynamically in the code
behind.
Click to expand...

If you've already created a static table, that's fine. Then you add your
dynamic controls to the table cells you create dynamically.
Also, I have several LinkButtons to insert in my Table and the total
number
of instances depends on the query results (can be more than hundred). How
can I define the ID for the each instance and deal with them in the
following Select Case when I have hundred IDs ?
Click to expand...

You need to come up with some kind of naming scheme. Since you're dealing
with this server-side, you might consider adding some sort of logic to where
you retrieve the query results from (database table?), i.e. being able to
lookup the ID and the action and/or value to pass to the page you redirect
to. Does this make sense?
 
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