There is no row at ...

[Stijn Verrept]

I have this code so far:

private void Page_Load(object sender, System.EventArgs e)
{
if (!IsPostBack)
{
Panel2.Visible = false;
Panel1.Visible = true;
Label1.Text = "Logged in as: " + Session["VisitorsName"];
sqlConnection1.Open();
sqlFilesIDAdapter.SelectCommand.Parameters["@ID"].Value =
Session["VisitorsID"];
sqlFilesIDAdapter.Fill(filesIDData1,"Files");
DataGrid1.DataBind();
}
}

private void DataGrid1_SelectedIndexChanged(object sender,
System.EventArgs e)
{
Panel1.Visible = false;
Panel2.Visible = true;
Label2.Text =
filesIDData1.Tables["Files"].Rows[DataGrid1.SelectedItem.ItemIndex]["TP_
Name"].ToString();
}


Now when I click on a row I get: 'There is no row at ' and then the
number. If I remove the !IsPostBack condition it works. Why is this?

 

[Mark Fitzpatrick]

Because the data is loaded the first time into the grid, but the second time
you haven't loaded the data therefore the grid is empty when you change the
index. You could store the object in the Viewstate and then recover it on
further loads, though this can make for a rather large page as the Viewstate
data tends to bloat a page pretty well.


Hope this helps,
Mark Fitzpatrick
Microsoft MVP - FrontPage

 

[Stijn Verrept]

Because the data is loaded the first time into the grid, but the
second time you haven't loaded the data therefore the grid is empty
when you change the index. You could store the object in the
Viewstate and then recover it on further loads, though this can make
for a rather large page as the Viewstate data tends to bloat a page
pretty well.

Thanks Mark for your answer, I understand now. But what I don't get is
why I need to reload the data if all I do is show a field in a label?
Is it possible to do this client side?

 

[Guest]

I agree, I don't know that I would recommend the viewstate because it can get pretty large, depending on how much data you're talking about

One of the things I've done is if the page is not a postback then load the grid. On the SelectedIndexChanged event on the grid I do all the manipulation and whatever I need to do, then I do a response.redirect to that same page I'm already on. This works pretty well (I think) if you're programmatically doing something with the data and leaving the user out of any data manipulation. However, if you need the user to manipulate the data this won't work so well (I don't think)

HTH
Jeremy

 

[Guest]

Stijn

The reason you need to reload the data is because when a postback happens you loose all of data. I know it seems bizarre, but that's how the web works. Every HTTP request to a file (or page) acts like a brand new request, that's why in your pages you'll need to put in the appropriate checks to ensure the page is a PostBack or not

I'm not sure about working with the grid on the client though. But I hope this answers your question about why you need to reload the data

Jeremy

 

[Craig Deelsnyder]

Mark Fitzpatrick wrote:




Thanks Mark for your answer, I understand now. But what I don't get is
why I need to reload the data if all I do is show a field in a label?
Is it possible to do this client side?

If you are looking up a value in the same table you bound to, just
create some invisible/hidden columns with the other column values you
need later on.

 

[Stijn Verrept]

If you are looking up a value in the same table you bound to, just
create some invisible/hidden columns with the other column values you
need later on.

Aha! Thanks

I changed it to Label2.Text = DataGrid1.SelectedItem.Cells[1].Text; and
this works great. I also replaced the Dataset by a DataReader which
seems to speed it up some more