html table binding issue

Question

I have a function with the following code that binds a table dynamically. I am calling this function in the page load. After this method is called the table contains three columns: A checkbox, label, and textbox.

I also have a button control. When this button is clicked I am checking for the checked checkboxes inside the table and then inserting data into the database corresponding to checked checkbox.

The problem is that it is not storing the checked state of the checkbox when the button is clicked as the button click also calls page load, which calls the function below and hence all of the elements in the table are recreated.

I cant use Page.IsPostBack here because the table should be loaded when the button is clicked. If I write the below code inside if(!Page.IsPostBack) then on button click it is not finding any rows in the table

try
{
    ManageVIN objMngVin = new ManageVIN();
    DataTable tblVins = objMngVin.MyFunction(clientCode);
    if (tblAssociateFleet.Rows.Count > 1)
    {
        for (int i = 1; i <= tblAssociateFleet.Rows.Count - 1; i++)
        {
            tblAssociateFleet.Rows[i].Cells.Clear();
        }
    }
    if (tblVins != null && tblVins.Rows.Count > 0)
    {
        foreach (DataRow dr in tblVins.Rows)
        {
            HtmlTableRow tblRow = new HtmlTableRow();
            tblRow.Attributes.Add("class", "tblrow");
            HtmlTableCell tblCell1 = new HtmlTableCell();
            CheckBox chk = new CheckBox();
            chk.CssClass = "selctChk";
            if (!Page.IsPostBack)
            {
                chk.Checked = false;
            }
            tblCell1.Controls.Add(chk);
            HtmlTableCell tableCelll2 = new HtmlTableCell();
            Label lblVinVlaue = new Label();
            lblVinVlaue.Text = Convert.ToString(dr["VIN"]);
            tableCelll2.Controls.Add(lblVinVlaue);
            HtmlTableCell tableCell3 = new HtmlTableCell();
            TextBox txtVinVal = new TextBox();
            txtVinVal.CssClass = "textEntry";
            tableCell3.Controls.Add(txtVinVal);
            tblRow.Cells.Add(tblCell1);
            tblRow.Cells.Add(tableCelll2);
            tblRow.Cells.Add(tableCell3);
            tblAssociateFleet.Rows.Add(tblRow);
        }
    }
}

How can I deal with this problem?

score 1 · Accepted Answer · edited May 23 '17 at 11:48

1

You should do this in the Init or PreInit life cycle. PreInit is the preferred place for this according to MS. If you take a look at the ASP.NET page life cycle Load is a bit too late (specifically missing IPostBackDataHandler.LoadPostData which processes postback data of your checkbox clicks).

Also, this is similiar to this stack overflow question.

edited May 23 '17 at 11:48

Community

1
1

answered Dec 07 '11 at 15:27

scottheckel

9,106
1
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47

while calling the function from preinit it works fine for first time, but now i have a dropdown also OnSelectedIndexChange of which i am calling the same function the problem is after changing the value in dropdown and clicking the button the dropdown selected index changed to default in the function. – Mac Dec 08 '11 at 08:36

score 1 · Answer 2 · answered Dec 07 '11 at 15:31

It sounds like the way you are doing it is pretty close to correct.

However, I see one problem. You have a block that states:

if (!Page.IsPostBack)
{
  chk.Checked = false;
}

Remove that block completely. The problem is that on postback asp.net actually renders the page twice. On the first render, that line is killing the state of the checkbox.

I know Hexxagonal said to do this in the init or preinit part of the lifecycle, however, we have a LOT of pages that dynamically generate controls. For those we always handle the generation in page_load and it works perfectly.

Even after removing that block the results are same – Mac Dec 08 '11 at 08:40 — Mac, Dec 08 '11 at 08:40

html table binding issue

2 Answers2