Dynamically append rows to table

5 Sep 2007 7:27 AM

Gorgsenegger

Hi all,

I have an ASP.Net table to which I want to append a number of rows
dynamically, i.e. there is a list of users in the table, and I want to
add more users via clicking on a button "Add".

The problem is that I can create the new row on the server side and
append it to the table which shows up fine in the browser, but when I
add another user the row I added before disappears.

Initial state:

John          Doe
Jack          Xyz

Now I click the button "Add":

John          Doe
Jack          Xyz
Carl          Abc

When I click the button again, I still come up with only three rows in
the table, as the initial table that was shown when the page first
loaded only contained two rows, and every time I add a new row it
seems that it will be shown in the browser but the server will forget
about it...

How can I solve this problem, any ideas?

Thanks in advance & best regards

Tim

7 Sep 2007 7:21 PM

Dblood

I assume that the existing data (the first two rows) is actually in
the HTML and not being read from a database or other data source, and
further that you are not storing the new row's data in a database (or
anywhere for that matter). In order for you to get the desired
results, you have to store the information between postbacks, and then
read it back in during the page loads.   I don't generally use
datagrids and databinding. I prefer to create the tables manually by
doing exactly what you are doing. There may be a better way to do
this using a datagrid, but someone else will have to give you the
procedure.

You may choose to add the record to the db each time the user clicks
on the "Add User" button, or you may want to store up all their new
records and then save them all at once. Either is possible. I prefer
to add the record each time, but it's your call. Just remember that
whatever you choose to do, the data will need to be stored somewhere
if you plan to retrieve it the next time you open the page. A
postback is exactly that - reopening the page. Some controls' data
can be forced to persist by setting EnableViewState = True on the
control. HTML tables do not have the EnableViewState property.

Unless you ask me to, I won't dig into how to save records into a
database, but here's what you can do.

1. Save the record each time the user clicks "Add User"
As mentioned above, write code to add the user to the database in the
button's click event, then write to code to retrieve the user records
from the database during the page_load event. You can dynamically add
the existing records to the table the same way you are adding the new
row. FWIW, if you databind a datagrid, this all (displaying the
records) happens for you when the page reloads.

2. Save the new records all at the same time
You can create a hidden textbox on the form. When the user clicks
"Add User", you append the info to the hidden textbox's value. I
usually delimit the columns with a semicolon, and the rows with the
pipe character. Upon postback, Request.Params("[your hidden
textbox]") into a string variable and then split the string back into
an array (Split on the pipe char). Then when creating your HTML
table, you split each individual row on the semicolon into an array.
Then assign the innerhtml property of each HTMLTableCell to the values
in the array.

A quick example of that:

Dim i as int16

Dim myData as string
myData = Request.Params("txtHide")

Dim aryData() as string
aryData = Splt(myData, "|")

For i = 0 to aryData.length - 1

   Dim tr0 as New HTMLTableRow()
   Dim tc0a as New HTMLTableCell()      'user
   Dim tc0b as New HTMLTableCell()      'password

   Dim aryRow() as string
   aryRow = Split(aryData(i), ";")

   tc0a.innerhtml = aryRow(0)
   tc0b.innerhtml = aryRow(1)

   tr0.Cells.Add(tc0a)
   tr0.Cells.Add(tc0b)

   tblExisting.Rows.Add(tr0)

Next i

You'll need another "Save" button, but when it's clicked, just loop
through the array again and call the save procedure from within the
loop (like the first example).

This turned into a long drawn out explanation. I didn't intend for it
to be. Hope something in it helps.

Danny