Question

got a exception when exec the query in LinqPad

var allNewsInADay= (from t in Tnews where t.SendTime.Value.Year==2012 && 
    t.SendTime.Value.Month==8  && t.SendTime.Value.Day==20 select t);
allNewsInADay.Dump();

Exception: The member access ‘System.DateTime Value’ is not supported

if use .HasValue property: NotSupportedException: The member access 'Boolean HasValue' is not supported

—
i use MySql
and my purpose is to get all records in a specific day.

Answer 1

var rslt= (from t in Tnews 
           where t.SendTime.HasValue 
              && t.SendTime.Value.Year==2012 
              && t.SendTime.Value.Month==8  
              && t.SendTime.Value.Day==20 
           select t);

or

var someDate = new DateTime(2012,8,20);
var rslt= (from t in Tnews 
           where t.SendTime.HasValue  
              && t.SendTime.Value.Date==someDate 
           select t);

will help?

upd: you tried bad. just ran this:

class Program
{
    public class TNews
    {
        public DateTime? SendTime { get; set; }
        public string Id;
    }
    static void Main(string[] args)
    {
        var tnews = new TNews[]
        {
            new TNews { SendTime = new DateTime(2012,8,20), Id="2012-08-20" },
            new TNews { SendTime = new DateTime(2012,8,20,12,20,0), Id="2012-08-20 12:20" },
            new TNews { SendTime = new DateTime(2012,8,21), Id="2012-08-21" },
            new TNews { SendTime = null, Id="null" },
        };

        var someDate = new DateTime(2012, 8, 20);
        var rslt = (from t in tnews
                    where t.SendTime.HasValue 
                       && t.SendTime.Value.Date == someDate
                    select t);

        foreach (var t in rslt)
        {
            Console.WriteLine(t.Id);
        }
    }
}

output is:

2012-08-20
2012-08-20 12:20
Press any key to continue . . .