"Steve P" wrote:

> This really is a question for Datalist, since that is what I am primarily
> using; however it should apply to Datagrid as well.
>
> I would like to be able to assign the itemtemplate and edititemtemplate
> programmatically based on how the user would like the data layed out.  I have
> been able to achieve this by using creating a class that implements the
> ITemplate interface, however I soon realized the drawback in that custom
> classes do not save their viewstate by default.  Therefore I have to retrieve
> the data and assign the templates at every postback, which consumes resources
> and doesn't take advantage of the Viewstate properties of the
> datalist/datagrid.  I tried adding my custom template class to the viewstate,
> but the error was that the object had to be serializable.  I looked at this
> briefly but gave up due to time constraints.
>
> Having said all this, *ideally* what I would like is to be able to do is
> just have the html templates in separate files and then instantiate a class
> based on the user's preferred layout and assign it to the datalist.  I think
> this is possible somehow but I don't have the time to research it right now. 
> If anyone has done something like this before or would like to try, that
> would be great!!
>
> Thanks,
> Steve

"Steve P" wrote:

> Okay, I found out that you can also use Page.LoadTemplate("<filename>.ascx")
> to assign the templates programmatically:
>
> DataList1.ItemTemplate = Page.LoadTemplate("itemtemplate1.ascx");
>
> This allows you to store the templates in different files, and assign them
> dynamically based on user input.  However, there are still a few problems. 
> First, you can't seem to be able to set DataList1.ExtractTemplateRows = true
> when doing this, because this causes the DataList to require that there be an
> asp table and doesn't recognize that my itemtemplate1.ascx actually contains
> a table.  Second, and more importantly, postback is a major problem I've had
> with dynamically loading templates.  This goes for doing it using a custom
> class that implements ITemplate and by using Page.LoadTemplate.  It works
> fine if there are no command buttons.  But if you do use, for instance, an
> Edit button (commandname=edit), then it will not work.  The problem is that
> on the containing page (e.g. mydatalist.aspx), you want the page_load method
> to have the !IsPostBack requirement:
>
> if (!IsPostBack) {
>    DataSub();
> }
>
> private void DataSub() {
>    DataList1.DataSource = getDataSource();
>    DataList1.ItemTemplate = Page.LoadTemplate("itemtemplate1.ascx");
>    DataList1.DataBind();
> }
>
> Unfortunately, if you have the !IsPostBack requirement, the page will not
> load DataSub() again initially when you click the edit button, but also the
> DataList1_EditCommand(...) method will never fire either!!  The only way to
> get it to fire is to remove the !IsPostBack requirement; then, for some
> reason, the initial DataSub() will occur in page_load, and then the
> editcommand event will fire afterwards, followed by anothere DataSub(), which
> is totally inefficient:
>
> DataList1_EditCommand(object sender, System.EventArgs e) {
>    DataList1.EditItemIndex = e.Item.ItemIndex;
>    DataSub();
> }
>
> So, if you remove the DataSub() from the editcommand method, then DataSub
> only occurs once, but only BEFORE the edititemindex has been assigned.
>
> ARRRGHH!!!!
>
> Does anyone have a proven method to dynamically assigning templates for the
> datagrid/datalist???  If so please let me know!  :-)
>
> Thanks
>
> "Steve P" wrote:
>
> > This really is a question for Datalist, since that is what I am primarily
> > using; however it should apply to Datagrid as well.
> >
> > I would like to be able to assign the itemtemplate and edititemtemplate
> > programmatically based on how the user would like the data layed out.  I have
> > been able to achieve this by using creating a class that implements the
> > ITemplate interface, however I soon realized the drawback in that custom
> > classes do not save their viewstate by default.  Therefore I have to retrieve
> > the data and assign the templates at every postback, which consumes resources
> > and doesn't take advantage of the Viewstate properties of the
> > datalist/datagrid.  I tried adding my custom template class to the viewstate,
> > but the error was that the object had to be serializable.  I looked at this
> > briefly but gave up due to time constraints.
> >
> > Having said all this, *ideally* what I would like is to be able to do is
> > just have the html templates in separate files and then instantiate a class
> > based on the user's preferred layout and assign it to the datalist.  I think
> > this is possible somehow but I don't have the time to research it right now. 
> > If anyone has done something like this before or would like to try, that
> > would be great!!
> >
> > Thanks,
> > Steve

"Steve P" wrote:

> Okay, found the solution to the problem about the edit button not firing. 
> You have to assign the datalist templates in the page_init method as in the
> microsoft example at
> http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vbcon/html/vbgrfcreatingtemplatecolumnsdynamicallyindatalistwebservercontrol.asp.
>  However, now I have another problem in that the editcommand actually fires
> twice instead of just once.  If you copy the example code at the link above
> this is what you will find, unless there is something I'm doing wrong  I will
> make a new post.
>
> "Steve P" wrote:
>
> > Okay, I found out that you can also use Page.LoadTemplate("<filename>.ascx")
> > to assign the templates programmatically:
> >
> > DataList1.ItemTemplate = Page.LoadTemplate("itemtemplate1.ascx");
> >
> > This allows you to store the templates in different files, and assign them
> > dynamically based on user input.  However, there are still a few problems. 
> > First, you can't seem to be able to set DataList1.ExtractTemplateRows = true
> > when doing this, because this causes the DataList to require that there be an
> > asp table and doesn't recognize that my itemtemplate1.ascx actually contains
> > a table.  Second, and more importantly, postback is a major problem I've had
> > with dynamically loading templates.  This goes for doing it using a custom
> > class that implements ITemplate and by using Page.LoadTemplate.  It works
> > fine if there are no command buttons.  But if you do use, for instance, an
> > Edit button (commandname=edit), then it will not work.  The problem is that
> > on the containing page (e.g. mydatalist.aspx), you want the page_load method
> > to have the !IsPostBack requirement:
> >
> > if (!IsPostBack) {
> >    DataSub();
> > }
> >
> > private void DataSub() {
> >    DataList1.DataSource = getDataSource();
> >    DataList1.ItemTemplate = Page.LoadTemplate("itemtemplate1.ascx");
> >    DataList1.DataBind();
> > }
> >
> > Unfortunately, if you have the !IsPostBack requirement, the page will not
> > load DataSub() again initially when you click the edit button, but also the
> > DataList1_EditCommand(...) method will never fire either!!  The only way to
> > get it to fire is to remove the !IsPostBack requirement; then, for some
> > reason, the initial DataSub() will occur in page_load, and then the
> > editcommand event will fire afterwards, followed by anothere DataSub(), which
> > is totally inefficient:
> >
> > DataList1_EditCommand(object sender, System.EventArgs e) {
> >    DataList1.EditItemIndex = e.Item.ItemIndex;
> >    DataSub();
> > }
> >
> > So, if you remove the DataSub() from the editcommand method, then DataSub
> > only occurs once, but only BEFORE the edititemindex has been assigned.
> >
> > ARRRGHH!!!!
> >
> > Does anyone have a proven method to dynamically assigning templates for the
> > datagrid/datalist???  If so please let me know!  :-)
> >
> > Thanks
> >
> > "Steve P" wrote:
> >
> > > This really is a question for Datalist, since that is what I am primarily
> > > using; however it should apply to Datagrid as well.
> > >
> > > I would like to be able to assign the itemtemplate and edititemtemplate
> > > programmatically based on how the user would like the data layed out.  I have
> > > been able to achieve this by using creating a class that implements the
> > > ITemplate interface, however I soon realized the drawback in that custom
> > > classes do not save their viewstate by default.  Therefore I have to retrieve
> > > the data and assign the templates at every postback, which consumes resources
> > > and doesn't take advantage of the Viewstate properties of the
> > > datalist/datagrid.  I tried adding my custom template class to the viewstate,
> > > but the error was that the object had to be serializable.  I looked at this
> > > briefly but gave up due to time constraints.
> > >
> > > Having said all this, *ideally* what I would like is to be able to do is
> > > just have the html templates in separate files and then instantiate a class
> > > based on the user's preferred layout and assign it to the datalist.  I think
> > > this is possible somehow but I don't have the time to research it right now. 
> > > If anyone has done something like this before or would like to try, that
> > > would be great!!
> > >
> > > Thanks,
> > > Steve