Creating controls dynamically based on user input

  • Thread starter Thread starter mohaaron
  • Start date Start date
M

mohaaron

I can think of a lot of reasons why this might need to be done but as
far as I can tell it's not possible. I've been looking for a way to
add HtmlTableRows to a table using a button click for a while and it
seems it's not possible because the row that gets added with each
click won't get recreated after a post back. After all the reading it
seems that any dynamically created controls must be created in the
Init event to be recreated after postback. This I think is very
unfortionate as it makes it impossible to change the display
interactively. Can someone please verify that this really is
impossible to do?
 
OK, I'll verify that you are on the right track. You will need to
recreate the number of rows you dynamically created during init. But,
once you've done that view state should be able to recreate everything
else.

"Any dynamically created controls must be created in Init to be
recreated after postback." Would be better stated, "Any dynamically
created control must be recreated in Init to have its state reset after
postback." Viewstate assumes the control object has been created, it is
just resetting the state of that object. Not, recreating the object AND
setting the state.

All you really need is a way to keep track of what you created
dynamically so that you can recreate it during init. You could do this
with a hidden field which you could get from
Request.Form["hiddenFieldName"] during Init.


-----Original Message-----
From: (e-mail address removed) [mailto:[email protected]]
Posted At: Tuesday, October 30, 2007 7:44 PM
Posted To: microsoft.public.dotnet.framework.aspnet
Conversation: Creating controls dynamically based on user input
Subject: Creating controls dynamically based on user input

I can think of a lot of reasons why this might need to be done but as
far as I can tell it's not possible. I've been looking for a way to
add HtmlTableRows to a table using a button click for a while and it
seems it's not possible because the row that gets added with each
click won't get recreated after a post back. After all the reading it
seems that any dynamically created controls must be created in the
Init event to be recreated after postback. This I think is very
unfortionate as it makes it impossible to change the display
interactively. Can someone please verify that this really is
impossible to do?
 
I don't think you are on the right track. You shouldn't need to build any
table dynamically. Instead, you should use one of the databound controls
that produce tables, like GridView, DataList or Repeater. You need to define
a datasource that will contain items (rows) holding data that will go to the
resulting table rows. When you databind the control to the datasource, it
will build the table for you automatically. The datasource doesn't have to
be a database table. It can be any collection object, like an array etc.
Based on user input, modify the datasource object, re-bind the control and
you are done.

--
Eliyahu Goldin,
Software Developer
Microsoft MVP [ASP.NET]
http://msmvps.com/blogs/egoldin
http://usableasp.net
 
If I shouldn't need to create a table dynamically then how would you
create a table which will have a undetermined number of rows? Meaning
the number of rows needs to change based on what the user needs. In my
case I have to allow the user the ability to create a new row of
information based on a button click. I keep trying to think of ways
around this problem and am now thinking maybe it's possible to pre-
create my table in the Init event with more rows then will be needed,
then set all the rows except the first one to Visible=False. Then as
the user needs another row I will just make it visible. This might
work. It's a hack as it will be a problem if the user needs more rows
then were provided.

I'm also thinking maybe I can do this using pure html and the
Request.Form method to custom build what I need.

There must be some way to do this.

I don't think you are on the right track. You shouldn't need to build any
table dynamically. Instead, you should use one of the databound controls
that produce tables, like GridView, DataList or Repeater. You need to define
a datasource that will contain items (rows) holding data that will go to the
resulting table rows. When you databind the control to the datasource, it
will build the table for you automatically. The datasource doesn't have to
be a database table. It can be any collection object, like an array etc.
Based on user input, modify the datasource object, re-bind the control and
you are done.

--
Eliyahu Goldin,
Software Developer
Microsoft MVP [ASP.NET]http://msmvps.com/blogs/egoldinhttp://usableasp.net




I can think of a lot of reasons why this might need to be done but as
far as I can tell it's not possible. I've been looking for a way to
add HtmlTableRows to a table using a button click for a while and it
seems it's not possible because the row that gets added with each
click won't get recreated after a post back. After all the reading it
seems that any dynamically created controls must be created in the
Init event to be recreated after postback. This I think is very
unfortionate as it makes it impossible to change the display
interactively. Can someone please verify that this really is
impossible to do?- Hide quoted text -
Click to expand...

- Show quoted text -
Click to expand...
 
If I shouldn't need to create a table dynamically then how would you
create a table which will have a undetermined number of rows?
Click to expand...

The point is that you add rows to the datasource which could be as simple as
just an array or an ArrayList. Than you do something like myGrid.DataBind()
and you get a table with as many rows as the number of items in your
datasource.

--
Eliyahu Goldin,
Software Developer
Microsoft MVP [ASP.NET]
http://msmvps.com/blogs/egoldin
http://usableasp.net
 
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