SelectList checkbox

My application is MVC 5, trying to develop multiselect checkbox using the following:

public static Dictionary<int, string> AdditionalInfo = new Dictionary<int, string>()
        {
            { 1, "Exercise" },
            { 2, "Diet" } 
        };

        public static int MapAdditionalInfo (string value)
            {
            return (from v in AdditionalInfo
                    where v.Value == value
                    select v.Key).FirstOrDefault();
            }

        public static string MapAdditionalInfo (int? value)
            {
            return (from v in AdditionalInfo
                    where v.Key == value
                    select v.Value).FirstOrDefault();
            }

        public string AdditionalInfo
            {
            get {  return MapAdditionalInfo(AdditionalInfoID); }
            set {  AdditionalInfoID = MapAdditionalInfo(value); }
            }

In the View:

   @foreach (SelectListItem item in (IEnumerable<SelectListItem>)ViewData["Info"] )
      {
         <label><input value="@item.Value" name="AdditionalInfoID" id="AdditionalInfoID" type='checkbox' checked="@item.Selected" class="checkbox-inline" /><span class='lbl padding-4'>@item.Value </span></label>
      }

In the controller:

ViewData["Info"] = MyModel.AdditionalInfo;

I get the following error:

Unable to cast object of type 'System.Collections.Generic.Dictionary`2[System.Int32,System.String]' to type 'System.Collections.Generic.IEnumerable`1[System.Web.Mvc.SelectListItem]'.

Would appreciate your suggestions on how to solve this error or if there a example for a better way to develop a checkbox list.