c# - LINQ to Entities 不支持“TimeOfDay” - 在 Linq 2 SQL 中查找总秒数

Question

当我执行以下操作时:

[EdmFunction("Edm", "TruncateTime")]
public static DateTime? TruncateDateTime(DateTime? inputDate)
{
    return inputDate.HasValue ? inputDate.Value.Date : (DateTime?)null;
}

 [EdmFunction("Edm", "TotalSeconds")]
public static double? GetTotalSeconds(DateTime? inputDate)
{
    return inputDate.HasValue ? inputDate.Value.TimeOfDay.TotalSeconds: (double?)null;
}

var employeeSelection = (from c in MyContext.Employees.Where(c => c.From.HasValue && c.To.TimeOfDay.TotalSeconds != 0)
...
select new Employee

{


 To = c.To != DateTime.MinValue && c.To.TimeOfDay.TotalSeconds != 0 ? TruncateDateTime(c.To).Value :
              c.To != DateTime.MinValue && c.To.TimeOfDay.TotalSeconds == 0 ? c.From.Value.AddMinutes(30) :  DateTime.MinValue

}

我明白了:

Additional information: The specified type member 'TimeOfDay' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.

当我尝试这个时:

var employeeSelection = (from c in MyContext.Employees.Where(c => c.From.HasValue && GetTotalSeconds(c.To) != 0)
...
select new Employee

{


 To = c.To != DateTime.MinValue && GetTotalSeconds(c.To) != 0 ? TruncateDateTime(c.To).Value :
              c.To != DateTime.MinValue && GetTotalSeconds(c.To) == 0 ? c.From.Value.AddMinutes(30) :  DateTime.MinValue

}

我明白了:

Additional information: The specified method 'System.Nullable1[System.Double] GetTotalSeconds(System.Nullable1[System.DateTime])' on the type 'GetDateRangeMethod' cannot be translated into a LINQ to Entities store expression.

如何查找 Linq to SQL 中的总秒数？

谢谢

Answer 1

尝试使用SqlFunctions.DatePart .

例如而不是

var employeeSelection = (from c in MyContext.Employees
          .Where(c => c.From.HasValue && GetTotalSeconds(c.To) != 0)

尝试类似的事情

var employeeSelection = (from c in MyContext.Employees
          .Where(c => c.From.HasValue && SqlFunctions.DatePart("second", c.To) != 0)

对于网络法师

var employeeSelection = (from c in MyContext.Employees
          .Where(c => c.From.HasValue && (SqlFunctions.DatePart("second", c.To) + (60 * SqlFunctions.DatePart("minute", c.To)) + (3600 * SqlFunctions.DatePart("hour", c.To))) != 0)

哪里

TotalSeconds = (SqlFunctions.DatePart("second", c.To) + (60 * SqlFunctions.DatePart("minute", c.To)) + (3600 * SqlFunctions.DatePart("hour", c.To)))