向位置x的动态ASP.NET表控件中添加新行-回发后Viewstate的问题

Question

I am creating a dynamic table control with ASP.NET/C# and the table is being used to hold a form. I need to allow users to click on a button in a row and make a duplicate of that row right below the original. My page is also using AJAX and jQuery.

I have tried to use Table.Rows.AddAt(indexoforigrow+1, newrow) but I get an error that the index is out of the range of values. I figured maybe I wasn't getting the original row's index correctly so I just tossed in a 1 and still got the error.

I also noticed that when I press the button to execute the code, the table disappears. Any ideas on how to fix that?

I am thinking that if I am unable to get these issues fixed I will have to loop through the table and submit the data to a temp table, adding a new row where indicated. Then I would pull all of the data back out and display again.

EDIT

I moved on when I could not get this working and tried to setup my submit functions to loop through the data and submit it to a db and realized that I am experiencing the same issues when clicking the submit button as when I click the add row button. It appears that my issue is really with viewstates/postback.

I did some reading on this and from what I can tell the solution is to re-create the dynamic control on page load every time. But I am confused about how I can do this if I have no idea how many rows/cells I have and how is the information the user entered kept in the form? I have no way of saving the information to a DB or anything because as soon as submit is clicked it all disappears.

Answer 1

Have you considered using a different control? One of the grid controls might better serve your purpose.

I've handled situations (that sound) similar to what you're describing by using the footer of a GridView (among other ways). The big trick is to bind the display object (Table, GridView, etc.) to a list of objects. Then you manipulate the list of objects, rebinding the display object after the list has changed.

You will need to persist this list in some manner, or you could wind up with the list being reset to null. One way would be to save it as part of the session.

At any rate, the idea is to have a display object (GridView) bound to a list of objects. When the user clicks 'add', an item is added to the list. Save the list, then call the GridView.DataBind method.

Answer 2

You are on the right track with re-creating the dynamic table each time the page loads. I have dome similar things and my solution was to keep a client state in a hidden field on the page. Every time you add a row to the table on the client, increment a counter or adjust the state data in the hidden field. Then, on the server-when the page posts back, read from that hidden field to know how many rows were added on the client. You will have to use some kind of naming convention for the new rows you add(and the widgets in them) so you can re-create them on the server.

A simpler option may be to use an UpdatePanel. Rather than try to add the rows on the client, your "add row" button would cause a partial update. The server side code would add the new row to the table and the viewstate would be updated.

Answer 3

I ended getting my data guy to do a bit more processing on his end so that I could just bind a ListView to a sproc. Solved a few of my problems.

Thanks for the helpful comments.

Answer 4

Just returning to this almost a year later because I faced a similar issue in my current project. I was doing a few things wrong my first time around. First, I did indeed need to recreate the controls every load, but I also had to create them earlier in the page cycle. I was trying to create them during page load, which is after the viewstate is loaded.

The controls need to be recreated with the same ID before viewstate is loaded. I went with page init and it worked fine.