Why am I getting this error message?

See more:

C#7.0

When I execute, I get this error message.

DateTime date = DateTime.Parse(sdate);
"String is not a valid DateTime"

public ActionResult DownloadFile(string sdate)
       {
           string filecontent = string.Empty;

           //changed iFTDTLContext to IFTDTLEntities
           using (var context = new Models.AFMESEntitiesContext())
           {

               DateTime date =  DateTime.Parse(sdate);

               //changed Admits to Files
               //changed file to files
               var results = (from f in context.BlindResults
                              where f.ExtractDate.Value.Year == date.Year && f.ExtractDate.Value.Month == date.Month && f.ExtractDate.Value.Day == date.Day
                              select f).ToList();

               filecontent = CreateDelimitedData(results);
           }

What I have tried:

I tried changing the format but still get the message. Can anyone help?