Bind multiple dropdownlists to same datasource using loop - asp.net

Question

I have a form with 15 dropdownlists inside a table. I would like populate each ddl with the same values from a single datasource.
Instead of doing the below x 15:
ddl.datasource = x
ddl.databind()
Is it possible to loop through all the DDL's in a table and assign the datasource etc all in one go?
Something like this? (I know the code is wrong but I am unsure of the full correct code)
For Each ctrl In tblNetwork.Controls
If TypeOf ctrl Is DropDownList Then
ddl.DataSource = usr
ddl.DataBind()
End If
Next ctrl
Seems a basic one but it's got me stumped.

Answer 1

You are getting stumped because your method is only going to traverse the top-level controls since iterating over tblNetworks.Controls won't be recursive.
I think that this is, in general, a very bad idea because your page will suffer from the recursion that you need to make in order to catch all the dropdowns in the page. With that said, here's a solution (in C#, sorry) that will work, regardless of the level of nesting of your dropdown lists.
First, you need to create a helper method that flattens any IEnumerable so we can use LINQ:
public static class ControlExtensions
{
public static IEnumerable<T> Flatten<T>( this IEnumerable<T> e, Func<T, IEnumerable<T>> f)
{
return e.SelectMany(c => f(c).Flatten(f)).Concat(e);
}
}
And now your code becomes this:
var result = this.Controls.Cast<DropDownList>().Flatten(x=>x.Controls.Cast<DropDownList>());
DropDownList current;
foreach (var item in result)
{
if (item is DropDownList)
{
current = item as DropDownList;
current.DataSource = your_data_source;
current.DataBind();
}
}
You can obviously extend this further to do the same on any page you need to, but the more complicated your page is, the bigger your performance hit.
I hope I persuaded you from doing this...