Cascading dropDownLists in repeater. DropDownLists with SQL source and add/delete option

Question

What is the trick to implement the following interface in ASP.NET?

I think the screenshot should explain everything.

1. Both dropDownLists work on SQL tables. [Categories],[Items] bound with ID_category PK/FK
2. Number of rows variable (by default 1 row with "Add" button)
3. Choosing category changes only the content of the dropDownList next to it and the content stays the same when other rows get added/deleted
4. "Add" button saves current setup and adds new row with either "Select value" or eventually 1st category/1st item selected

How to store previously selected categories/items and the dropDown filtering by category, while adding, changing, deleting items or some other PostBack on website?

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What I have tried so far is to use Repeater with DataSet, however I have encountered several different problems:

• Was unable to preserve the relations between previous dropDowns
• DropDowns resetting one another
• 2nd dropDown losing filtering when adding new row

I can post some code but since it doesn't fully work, perhaps a totally different approach would be better. Basically I started with this tutorial. The repeater currently looks like:

<repeater>
<itemtemplate>
  <dropDown DataSource="categoriesDS" 
     value='<%# DataBinder.Eval(Container.DataItem, "Category") %>'.../>
  <dropDown DataSource="itemsDS" 
     value='<%# DataBinder.Eval(Container.DataItem, "Item") %>'.../>
  <button CommandName='<%# DataBinder.Eval(Container.DataItem, "Button") %>' 
     Text='<%# DataBinder.Eval(Container.DataItem, "Button") %>' .../>
</itemtemplate>
</repeater>

Thanks in advance for any suggestions or solutions and I hope it'll be helpful for others.

Answer 1

Ajax Cascading DropDownlist

It is very simple to use.