binding - DropDownList flaw/bug?

24 Jun 2005 6:43 PM

Matthew.DelVecchio

hey gang,

ok so i experienced something that doesnt operate as i would have
expected. in a component i build up a ListItemCollection in function
..GetGalleries() like so:

Dim galleries As New System.Web.UI.WebControls.ListItemCollection

   'loop & add to collection
   Dim node As XmlNode
   For Each node In galleryNodes
      galleries.Add(New ListItem("sometext", "somevalue"))
   Next

   Return galleries

then, in my application i attempt to bind like so:

   Dim galleries As ListItemCollection = im.GetGalleries(year)

   ddlGallery.DataSource = galleries
   ddlGallery.DataBind()

....now, you would think then, that the ddlGallery dropdownlist would
take the returned ListItemCollection and bind its list items to the
list. It does -- sort of.. it does, BUT it doesnt use the ".value"
porton of the returned ListItems ("somevalue"). instead, it just takes
the ".text" value of each ListItem ("sometext") and sticks that in both
the text AND the value of each item in ddlGallery. whaaaa?

clearly, the expected behavior would be for ddlGallery list control to
see that its getting a ListItemCollection as a datasource, and
intelligently bind it -- by using the existing .text and .value values
if of the collection's ListItems... after all, this isnt any ole
collection, it's a *ListItemCollection*...!

as a work around, i have to loop thru the returned collection and add
each individually, like so:

   Dim galleries As ListItemCollection = im.GetGalleriesForYear(year)

   Dim item As ListItem
   For Each item In galleries
      ddlGallery.Items.Add(item)
   Next

thats pretty lame. can anyone comment on this?

thanks!
matt

--
Matt Del Vecchio

24 Jun 2005 8:25 PM

Harolds

try this
ddlGallery.DataSource = galleries
ddlGallery.DataTextField = "Text"
ddlGallery.DataValueField = "Value"
ddlGallery.DataBind()

Show quoteHide quote

"Matthew.DelVecc***@CapitalOneAuto.com" wrote:

> hey gang,
>
> ok so i experienced something that doesnt operate as i would have
> expected. in a component i build up a ListItemCollection in function
> ..GetGalleries() like so:
>
>
> Dim galleries As New System.Web.UI.WebControls.ListItemCollection
>
>    'loop & add to collection
>    Dim node As XmlNode
>    For Each node In galleryNodes
>       galleries.Add(New ListItem("sometext", "somevalue"))
>    Next
>
>    Return galleries
>
> then, in my application i attempt to bind like so:
>
>    Dim galleries As ListItemCollection = im.GetGalleries(year)
>
>    ddlGallery.DataSource = galleries
>    ddlGallery.DataBind()
>
> ....now, you would think then, that the ddlGallery dropdownlist would
> take the returned ListItemCollection and bind its list items to the
> list. It does -- sort of.. it does, BUT it doesnt use the ".value"
> porton of the returned ListItems ("somevalue"). instead, it just takes
> the ".text" value of each ListItem ("sometext") and sticks that in both
> the text AND the value of each item in ddlGallery. whaaaa?
>
> clearly, the expected behavior would be for ddlGallery list control to
> see that its getting a ListItemCollection as a datasource, and
> intelligently bind it -- by using the existing .text and .value values
> if of the collection's ListItems... after all, this isnt any ole
> collection, it's a *ListItemCollection*...!
>
> as a work around, i have to loop thru the returned collection and add
> each individually, like so:
>
>    Dim galleries As ListItemCollection = im.GetGalleriesForYear(year)
>
>    Dim item As ListItem
>    For Each item In galleries
>       ddlGallery.Items.Add(item)
>    Next
>
>
>
> thats pretty lame. can anyone comment on this?
>
> thanks!
> matt
>
> --
> Matt Del Vecchio
>
>

25 Jun 2005 12:19 AM

Matthew.DelVecchio

ah... yes im familar with those properties, however i thought they only
pertained to the string name of a data column, say from a dataset or
datatable -- i didnt realize they would accept "Text" and "Value"..!
that is cool and saves me code. thanks.

case closed!

now, does that work only because the ListItemCollection uses "Text" and
"Value" as internal names? meaning, can this work with say a
multi-dimensional array, or dictionary object, etc -- other collection
objects of 2-part items? probably not, because those collection types
dont have "Text" or "Value" -- in which case, how do we designate...

what im really getting at, is an XML nodelist... say if i bind a
nodelist to a DropDownList, im not aware of a way -- even using
..DataTextFile & .DataValueField -- to designate which peices of data it
should use.

for ex:

<people>
    <person id="1" name="Joe">[blah]</person>
    <person id="2" name="Bob">[blah]</person>
    <person id="3" name="Roberto">[blah]</person>
</people>

....you can successfully use this nodelist as a .DataSource, but i
havent figured out a way to specificy which elements of the data to use
for what.

thanks,
matt