Question

我正在寻找以下linq查询和扩展方法的帮助：

DateTime? ddStartOfTime = Convert.ToDateTime("2016/04/10 11:15:00");
DateTime? ddEndOfTime = Convert.ToDateTime("2017/06/25 13:15:00");

List<int> doWeeksNeeded = new List<int>();

doWeeksNeeded.Add(201614);
doWeeksNeeded.Add(201616);

var dq1 = (from c in tblschedulefulldates
       where doWeeksNeeded.Contains(c.ddJobStart.GetYearWeekFormat())
       orderby c.diEmployeeID
       select new
       {
           diEmployeeID = c.diEmployeeID == null ? 0 : (int)c.diEmployeeID,
           dnDayOfWeek = c.ddJobStart.DayOfWeek == null ? 0 : (int)c.ddJobStart.DayOfWeek
       });

以下是扩展方法：

public static int GetYearWeekFormat(this DateTime pddate)
{
    int weekNo = GetIso8601WeekOfYear(pddate);
    int year = pddate.Year;
    if (weekNo == 1 && pddate.Month > 1) year = year + 1;
    return Convert.ToInt32(year.ToString() + weekNo.ToString().Trim());
}

public static int GetIso8601WeekOfYear(this DateTime pddate)
{
    System.Globalization.Calendar cal = System.Globalization.CultureInfo.InvariantCulture.Calendar;
    // Seriously cheat.  If its Monday, Tuesday or Wednesday, then it'll 
    // be the same week# as whatever Thursday, Friday or Saturday are,
    // and we always get those right
    System.DayOfWeek day = cal.GetDayOfWeek(pddate);
    if (day >= System.DayOfWeek.Monday && day <= System.DayOfWeek.Wednesday)
    {
        pddate = pddate.AddDays(3);
    }

    // Return the week of our adjusted day
    return cal.GetWeekOfYear(pddate, System.Globalization.CalendarWeekRule.FirstFourDayWeek, System.DayOfWeek.Monday);
}

然而，当我跑步时，我得到：

Method 'Int32 GetYearWeekFormat(System.DateTime)' has no supported translation to SQL

所以我决定创建另一个名为In：

的扩展

public static bool In<T>(this DateTime value, IEnumerable<Int32> values)
{
    if (values == null)
        throw new ArgumentNullException("values");
    int lnWeek = GetYearWeekFormat(value);
    return values.Contains(lnWeek);
}

并称之为：

var dq1 = (from c in tblschedulefulldates
       where c.ddJobStart.In(doWeeksNeeded)
       orderby c.diEmployeeID
       select new
       {
           diEmployeeID = c.diEmployeeID == null ? 0 : (int)c.diEmployeeID,
           dnDayOfWeek = c.ddJobStart.DayOfWeek == null ? 0 : (int)c.ddJobStart.DayOfWeek
       });

除了我不能让这个工作。它给出了以下错误：

The type arguments for method 'DateTimeExtensions.In<T>(DateTime, IEnumerable<int>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

有人可以帮忙吗？

Answer 1

LINQ 2 SQL不知道如何将GetYearWeekFormat翻译成SQL。

您需要先查询数据库，然后在本地列表上进行工作。

var localList = (from c in tblschedulefulldates
   select new
   {
       ddJobStart= c.ddJobStart,
       diEmployeeID= c.diEmployeeID,
   }).ToList();

var dq1 = (from c in localList
       where doWeeksNeeded.Contains(c.ddJobStart.GetYearWeekFormat())
       orderby c.diEmployeeID
       select new
       {
           diEmployeeID = c.diEmployeeID == null ? 0 : (int)c.diEmployeeID,
           dnDayOfWeek = c.ddJobStart.DayOfWeek == null ? 0 : (int)c.ddJobStart.DayOfWeek
       });

Linq扩展方法 - GetYearWeekFormat扩展

1 个答案: