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table disappears

Hi,

I fill a Table from my code-behind file (C# ASP.NET 2.0) which is supposed to represent a form.

<asp:Table ID="input_table" runat="server" CellPadding=10 GridLines="Both" BackColor = white>
    </asp:Table>

The table is successfully created here:

protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            // create table

            … invoke code to create the table

            Session["input_table"] = this.input_table;
}
else
{

}
}

The table is made persistent as shown above. The page also contains a button. In its OnClick method I would like to access the entries of the user (in the table cells). Unfortunatley, the table disappears  when the button is clicked. I am just wondering why this is and how I can prevent it? Any input would be very much appreciated. Many thanks in advance.

Chris
0
csetzkorn
Asked:
csetzkorn
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1 Solution
 
ethothsCommented:
You need to get the table back out of session state in your else clause (if it is a postback).

this.input_table=Session["input_table"]


0
 
csetzkornAuthor Commented:
sorry, I did this but forgot to add it to my post. I seem to be able to access the table in the OnClick method but it disappears.

C
0
 
csetzkornAuthor Commented:
Hi,

It still disappears. Any feedback would be very much appreciate. This is the 'correct code' I am using:

protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
          // create table

          … invoke code to create the table

          Session["input_table"] = this.input_table;
}
else
{
this.input_table = (Table)Session["input_table"];
}
}
0
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ethothsCommented:
You are creating the tabel in the if clause. Are you also adding it to the pages controls collection here. If so you need to do this in the else clause also. Please send your complete code.
0
 
csetzkornAuthor Commented:
The table already exists in the aspx file

<asp:Table ID="input_table" runat="server" CellPadding=10 GridLines="Both" BackColor = white>
</asp:Table>

In Page_Load I add objects (e.g. TextBox[es]) to the table cells. This works fine. The table is shown like a form with all these elements. When I click this button:

<asp:Button id="validate_entries" Runat="server" Font-Bold="True" Text="Validate Entries" OnClick="validateEntriesClick"></asp:Button>
   
I can still access all the objects in the table within the 'validateEntriesClick' method but the table becomes invisible. The question is why this happens? This:

this.input_table = (Table)Session["input_table"];

does not seem enough to make it reappear. Perhaps I do not fully understand the life cycle of the page but I doubt I have to recreate everything ...

Thanks,

C
0
 
csetzkornAuthor Commented:
If I am using:

protected void Page_Load(object sender, EventArgs e)
{
         // create table

          … invoke code to create the table
}

everything works fine (I even don't lose the data entered by the user???). However, this would be too inefficient wouldn't it as the table is created every time ...??!!

C
0
 
Bob LearnedCommented:
If you are adding the Table dynamically, all dynamic controls need to be recreated on post-back.

Bob
0
 
csetzkornAuthor Commented:
This might be a stupid question. Why can I not put the whole (dyn. created) object (table), which contains all the other objects, and put it in a session object and then (after the postback) do this:

Session["input_table"] = this.input_table;

as I have done before.

Everything works fine if I recreate the table each time after a postback. I am just wondering, why ASP.NET 2.0 is 'clever enough' to restore the values entered by a user (they are still their after a postback).

Thanks.

Christian
0
 
Bob LearnedCommented:
You can store anything serializable into the Session, but that doesn't mean that it is added to the form through that mechanism.  It needs to be rendered in the output HTML.

Bob
0
 
csetzkornAuthor Commented:
ok thanks. that makes sense.

could you possibly answer the second part of my last question?

Thanks.

C
0
 
Bob LearnedCommented:
If you are storing the Table in the Session, on post back are you recreating the Table, or getting it from the Session variable and rendering that?

Bob
0
 
csetzkornAuthor Commented:
no. I am just doing this:

protected void Page_Load(object sender, EventArgs e)
{
         // create table

          … invoke code to create the table
}

and it works as I wanted. It even persists the values entered by users (e.g. after a refresh). I am just wondering why this is? ASP.NET 2.0 seems to do this automatically which is nice.

Thanks,

Christian
0
 
ethothsCommented:
Yes asp.net does this automatically. It can even raise echanged events as it knows what the previous values was (from viewstate) and it knows what the new values is (from the post collection).

 
0
 
csetzkornAuthor Commented:
Ok thanks for your feedback. I accept Bob's comment (11/08/2006 04:54AM PST
) as it clarifies things.

Chris
0

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