LINQ to Entities无法识别方法'System.DateTime ToDateTime（System.String）'

Question

I have a column TG003 to store date which is a string.

And I want to list data for the past seven days

Below is what I have done and I'm having errors:

LINQ to Entities does not recognize the method 'System.DateTime ToDateTime(System.String)' method, and this method cannot be translated into a store expression.

public List<CCOPTG> listrecentCCOPTG()
{
    string startdate = DateTime.Today.AddDays(-7).ToString("yyyyMMdd");
    string enddate = DateTime.Now.ToString("yyyyMMdd");
    return db.CCOPTG.Where(p => Convert.ToDateTime(p.TG003)>=Convert.ToDateTime(startdate) && Convert.ToDateTime(p.TG003) <= Convert.ToDateTime(enddate)).OrderByDescending(p=>p.TG003).ToList();
}

Please advise.

Answer 1

Try try following

public List<CCOPTG> listrecentCCOPTG()
{
    datetime startdate = DateTime.Today.AddDays(-7);
    datetime enddate = DateTime.Now;
    return db.CCOPTG.Where
        (p => p.TG003>=startdate && p.TG003 <= enddate)
        .OrderByDescending(p=>p.TG003).ToList();
}

LINQ does not recognise conversion functions so do your conversions first.

Answer 2

I've created a sample that runs in LinqPad without any errors.

void Main()
{
       List<CCOPTG> list = new List<CCOPTG>();

      for (DateTime i =DateTime.Today.AddDays(-20); i <DateTime.Today; i=i.AddDays(1))
      {
        list.Add(new CCOPTG { TG003 = i.ToShortDateString()});
      }

    listrecentCCOPTG( list);
}

public class CCOPTG
{
public string TG003 { get; set;}

}
// Define other methods and classes here
public static void listrecentCCOPTG(List<CCOPTG> list)
{
DateTime startdate = DateTime.Today.AddDays(-7);
DateTime enddate = DateTime.Now;
 list.Where
    (p => DateTime.Parse(p.TG003) >= startdate && DateTime.Parse(p.TG003) <= enddate)
    .OrderByDescending(p => p.TG003).ToList().Dump();
}

This produced the following result:

2/5/2017
2/4/2017
2/3/2017
2/2/2017
2/1/2017
1/31/2017
1/30/2017