How can I convert List<object> to Hashtable in C#?
Let's assume that your List contains objects of type Foo (with an int Id and a string Description).
You can use Linq to turn that list into a Dictionary like this:
var dict = myList.Cast<Foo>().ToDictionary(o => o.Description, o => o.Id);
If you have access to Linq, you can use the ToDictionary function.