Linking events from controls, when the controls have been created - DOTNET

when you create the control just add the handler

myImage.OnClick += new ImageClickEventHandler(myImageClick);

to get the postback event, you need to recreate the controls (with the
same id's) in OnInit and assign the handlers


-- bruce (sqlwork.com)



rival@newsgroups.nospam wrote:
> I've a situation where I'm creating controls programatically. I'm
> programatically creating table cells and rows. I've got an array of data,
> and I want to format the data on screen in rows of 4. I get my array,
> calculate how many complete rows I need. Then for each of the complete rows,
> I format a cell for the data in that array element. When I've completed a
> row, I add it to my table. If I have a remainder, I do that at the end.
>
> This works very well. However, I want users to be able to select one of the
> images I'm showing by clicking on it. Normally, I would do this by
> <asp:Image ID="myImage" runat="server" OnClick="myImage_Click"/>
> and I would put the code into
> protected void myImageClick(object sender, EventArgs e)
> {
> Code Here
> }
>
> However, because I'm creating the ImageButton controls programatically, I
> can't quite get an event wired in. I've created event handlers, but I think
> that because each ImageButton class in created in FormatCell, then they are
> out of scope in a postback. Does anyone have a way for me to reliably wire
> an event handler into a programatically created control?
>
>
>
>
> The code is below
>
> protected void Page_Load(object sender, EventArgs e)
> {
> int typesPerRow = 4;
> if (!IsPostBack)
> {
>
> PointType[] types = PointSystem.GetPointTypes();
> TableRow tr;
>
> //Display the point types, four in a row.
> int rows = types.Length / typesPerRow;
> int remainder = types.Length % typesPerRow;
> for (int i = 0; i < rows; i++)
> {
> tr = new TableRow();
> for (int j = 0; j < typesPerRow; j++)
> {
> tr.Cells.Add(FormatCell(types[counter]));
> }
> emailPointTable.Rows.Add(tr);
> }
>
> //Do the last (partial) row
> if (remainder != 0)
> {
> tr = new TableRow();
> for (int j = 0; j < remainder; j++)
> {
> tr.Cells.Add(FormatCell(types[counter]));
> }
> emailPointTable.Rows.Add(tr);
> }
> }
>
>
> private TableCell FormatCell(PointType t)
> {
> ImageButtton pointPic;
> TableCell cell;
> LinkButton selectme;
>
> cell = new TableCell();
> cell.SkinID = "skinCell";
>
> pointPic = new ImageButton();
> pointPic.Click += new ImageClickEventHandler(this.pointTypeSelected);
> pointPic.SkinID = "skinImage";
> pointPic.ImageUrl = t.ImageLarge;
> pointPic.Height = 128;
> pointPic.Width = 128;
>
> selectme = new LinkButton();
> selectme.Text = t.Name;
> selectme.CommandName = "SelectPointType";
>
> cell.Controls.Add(pointPic);
> cell.Controls.Add(new LiteralControl("<br/>"));
> cell.Controls.Add(selectme);
>
> return cell;
> }

Hi rival

> However, because I'm creating the ImageButton controls programatically, I
> can't quite get an event wired in. I've created event handlers, but I
> think
> that because each ImageButton class in created in FormatCell, then they
> are
> out of scope in a postback. Does anyone have a way for me to reliably
> wire
> an event handler into a programatically created control?
you have to execute your code on every time, postback or not.
that means, place your code outside of if(!this.IsPostBack), then that
should work fine.

--
Gruss, Peter Bucher
Microsoft MVP - Visual Developer ASP / ASP.NET, Switzerland
http://www.aspnetzone.de/ - ASP.NET Zone, die ASP.NET Community
http://www.aspnetzone.de/blogs/peterbucher/ - Auf den Spuren von .NET

Thanks for this - firstly, Bruce - I'd already got the event linked in as you
described. "you need to recreate the controls (with the
same id's) in OnInit and assign the handlers" was the issue. I didn't want
to do a hundred object declarations in case I need the object! I think you
are driving at the same thing Peter has written below.
"you have to execute your code on every time, postback or not"

I've changed my Page_Load to this:
if (!IsPostBack)
{
emailPointTable.Visible = true;
}
else
{
emailPointTable.Visible = false;
}
PointType[] types = PointSystem.GetPointTypes();
TableRow tr;

//Display the point types, three in a row.
int rows = types.Length / typesPerRow;
int remainder = types.Length % typesPerRow;
int counter = 0;
for (int i = 0; i < rows; i++)
{
tr = new TableRow();
for (int j = 0; j < typesPerRow; j++)
{
tr.Cells.Add(FormatCell(types[counter]));
counter++;
}
emailPointTable.Rows.Add(tr);
}

//Do the last (partial) row
if (remainder != 0)
{
tr = new TableRow();
for (int j = 0; j < remainder; j++)
{
tr.Cells.Add(FormatCell(types[counter]));
counter++;
}
emailPointTable.Rows.Add(tr);
}

So if I'm posting back, I just don't render the table. And it works!
Fantastic help from both Bruce and Peter

Thanks again






"Peter Bucher [MVP]" wrote:

> Hi rival
>
> > However, because I'm creating the ImageButton controls programatically, I
> > can't quite get an event wired in. I've created event handlers, but I
> > think
> > that because each ImageButton class in created in FormatCell, then they
> > are
> > out of scope in a postback. Does anyone have a way for me to reliably
> > wire
> > an event handler into a programatically created control?
> you have to execute your code on every time, postback or not.
> that means, place your code outside of if(!this.IsPostBack), then that
> should work fine.
>
> --
> Gruss, Peter Bucher
> Microsoft MVP - Visual Developer ASP / ASP.NET, Switzerland
> http://www.aspnetzone.de/ - ASP.NET Zone, die ASP.NET Community
> http://www.aspnetzone.de/blogs/peterbucher/ - Auf den Spuren von .NET
>
>
>