Dropdownlist validation in Asp.net Using Required field validator

For MVC v5.1 use Html.EnumDropDownListFor

@Html.EnumDropDownListFor(
    x => x.YourEnumField,
    "Select My Type", 
    new { @class = "form-control" })

For MVC v5 use EnumHelper

@Html.DropDownList("MyType", 
   EnumHelper.GetSelectList(typeof(MyType)) , 
   "Select My Type", 
   new { @class = "form-control" })

For MVC 5 and lower

I rolled Rune's answer into an extension method:

namespace MyApp.Common
{
    public static class MyExtensions{
        public static SelectList ToSelectList<TEnum>(this TEnum enumObj)
            where TEnum : struct, IComparable, IFormattable, IConvertible
        {
            var values = from TEnum e in Enum.GetValues(typeof(TEnum))
                select new { Id = e, Name = e.ToString() };
            return new SelectList(values, "Id", "Name", enumObj);
        }
    }
}

This allows you to write:

ViewData["taskStatus"] = task.Status.ToSelectList();

by using MyApp.Common

You're correct in stating that you don't have the ViewState right, which is why the values aren't populated when you post the data back to the server.

I would strongly recommend that you migrate to using the Cascading Drop Down within the ASP.NET AJAX Control Toolkit (it has both .NET 2.0 and .NET 3.5 releases), as it does what you are after and it does maintain via the postback.

Your other option would be to have an onchange event on the JavaScript-populated drop down list in which you then populate a hidden field, as that will be posted back to the server and the value of the submit will be maintained within the posted data, something like:

$addHandler('change', $get('dynamicDDL'), function () { $get('hiddenField').value = this.options[this.selectedIndex].value; });

For the demo I used the MS AJAX short-hand for adding events, etc. More info on the methods I used can be found here: http://msdn.microsoft.com/en-au/library/bb397536.aspx