c# - 日期时间到字符串转换显示错误

Question

我正在尝试使用自定义格式将 DateTime 转换为 string。但它向我显示 LINQ 错误

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

这是我在 Controller 中的代码:

public ActionResult DaywiseData(DateTime date)
{
    try
    {
        var att = db.Attendances
                 .Where(d => d.Date == date)
                 .Select(s => new AttendanceViewModel
                  {
                      Date = s.Date,
                      aa = DateTime.Parse(s.InTime.ToString()).ToString("HH:mm tt"),  //Error is not showing after removing this line
                      InTime = s.InTime,
                      OutTime = s.OutTime,
                      EmployeeName = s.Employee.Name,
                      EmployeeUsername = s.Employee.Username
                  })
                  .ToList();
         return Json(att);
     }
     catch (Exception ex)
     {
         return Json(ex.Message);
     }
}

Answer 1

您的 LINQ 已转换为不支持 ToString() 的 SQL 查询。将其保留为 DateTime，稍后转换为字符串。像这样的事情

public ActionResult DaywiseData(DateTime date)
{
    try
    {
        var att = db.Attendances
                 .Where(d => d.Date == date)
                 .Select(s => new AttendanceViewModel
                  {
                      Date = s.Date,
                      DateTime = s.InTime, //dateTime property
                      DateTimeString = string.Empty //string property
                      InTime = s.InTime,
                      OutTime = s.OutTime,
                      EmployeeName = s.Employee.Name,
                      EmployeeUsername = s.Employee.Username
                  })
                  .ToList();
         att.ForEach(a => a.DateTimeString = a.DateTime.ToString("HH:mm tt"));

         return Json(att);
     }
     catch (Exception ex)
     {
         return Json(ex.Message);
     }
}