Custom DropZone for each row in a RadGrid
Description
The DropZones property of the AsyncUpload receives a CSS selector so in regular cases adding the ID of the dropzone element works perfectly.
In case you want to use the AsyncUpload in a TemplateColumn of the RadGrid and create a custom dropzone for each row, then using a plain ID for the dropzone would not work. This is because on the page, you will have many dropzones with the same ID.
Solution
The solution is to generate the ID of the DropZone based on the clientID of the row or the AsyncUpload itself. Here is a sample solution using Markup only. The same could be achieved in the code behind as well:
<ItemTemplate>
<telerik:RadAsyncUpload runat="server" ID="RadAsyncUpload1" DropZones='<%# new string[] { ".drop-zone-" + Container.ClientID }%>'></telerik:RadAsyncUpload>
<div id="DropZone1" class='<%# "DropZone1 drop-zone-" + Container.ClientID %>' runat="server">
Custom drop zone per row
</div>
</ItemTemplate>