I had code where I populate the contents of an ASP.NET DropDownList with a strongly typed DataTable returned from an ASP.NET web service. In this code I bound the DataTable to the DataSource of the DropDownList and did a DataBind() in the Page_Load() method. This worked perfectly fine on my local box.
However, when I loaded up the ASP.NET page in the production data center, I got:
DropDownList cannot have multiple items selected
To solve this problem, after I bound the DataTable to the DropDownList, I iterated through each ListItem and set its Selected property to false:
foreach (ListItem myItem in myDropDownList)
myItem.Selected = false;