Try this:
DateTime dFrom = new DateTime(20,4,2015);
DateTime dTo = new DateTime(27,4,2015);
var qry = datacontext
.Where(a=>a.TraDate>=dFrom && a.TraDate<=dTo)
.GroupBy(a=>a.TraDate.ToString("MM-dd-yyyy"))
.Select(grp=>new
{
Date = grp.Key,
CountOfApps = grp.Count()
});