LINQ to Entities无法识别MVC5中的方法'System.DateTime ParseExact（System.String，System.String，System.IFormatProvider）'方法错误

Question

Hi i have one view called DailyVisitReport . In that view i have two field called FromDate and toDate . if i select the FromDate and ToDate depends upon the date it shows the table with data in the same view (like partial view).

Now FromDate and ToDate date Format in jquery is "dd-My"(01-Mar-16)

In Db also i changed the Date format to (01-Mar-16 STRING).

My Model(VisitorsViewModel)

public DateTime FromDate { get; set; }
public DateTime ToDate { get; set; }
public ICollection<View_VisitorsForm> Visits { get; set; }

My Controller Code

public ActionResult GetDatesfromFromDateToDate(string fromDate, string toDate)
{
    CultureInfo provider = CultureInfo.InvariantCulture; 
    var fromdt = Convert.ToDateTime(fromDate);
    var  todt = Convert.ToDateTime(toDate);
    List<View_VisitorsForm> VisitCount = (from v in db.View_VisitorsForm where DateTime.ParseExact(v.VisitingDate,"dd-M-y", provider) >= fromdt && DateTime.ParseExact(v.VisitingDate,"dd-M-y",provider) <= todt select v).ToList();
    VisitorsViewModel visitotsVM = new VisitorsViewModel();
    visitotsVM.Visits = VisitCount;
    return PartialView("_Visitors", visitotsVM);
}

Now I select the FromDate and ToDate it show the error which is mention below

LINQ to Entities does not recognize the method 'System.DateTime ParseExact(System.String, System.String, System.IFormatProvider)' method

I cant able to convert that v.VisitingDate to DateFormat from string format .

I tried Convert.ToDateTime and Convert.ToParse all things. still I'm getting error. please any one understand my issue and help me to resolve this issue.

Answer 1

All the operations inside a Linq to Entities query are converted to sql. DateTime.Parse cannot be translated to sql thus the error.

Perform the parse outside the where to solve specifically that problem but, more generally, you should make VisitingDate a DateTime property too.

Answer 2

The property VisitingDate should be of type DateTime to avoid these struggles. Do not compare datetime values by using string mishmash, use DateTime types.

The where condition would then look like

where v.VisitingDate.HasValue ?
    v.VisitingDate.Value >= fromdt && v.VisitingDate.Value <= todt
  : 
    ... // put a condition here when visiting date has no value in DB

Also heres a list of supported / unsupported methods in LINQ to SQL, i assume the same goes for LINQ to Entities: https://msdn.microsoft.com/en-us/library/bb386970.aspx

Therefore you cannot use Parse....