无法使EntityFunctions.TruncateTime()工作

Question

我正在使用Entity Framework Code First.使用LINQ to Entity我想根据DateTime值获取记录.这是我目前的代码:

/// <summary>
/// A method to check and see if the Parsed Game already exists on the
/// database. If Yes, then True is returned, otherwise False is returned.
/// </summary>
/// <param name="context">The Db Context to use</param>
/// <param name="homeTeam">The Name of the Home Team for the Game.</param>
/// <param name="awayTeam">The Name of the Away Team for the Game.</param>        
/// <param name="date">The Date of the Game</param>
/// <returns></returns>
public bool doesGameAlreadyExist(PContext context, String homeTeam, String awayTeam, String date)
{
    string dtObjFormat = "dd MMM yyyy";
    DateTime dt;
    DateTime.TryParseExact(date, dtObjFormat, CultureInfo.InvariantCulture, DateTimeStyles.None, out dt);
    var result = context.Games.Where(x => EntityFunctions.TruncateTime(x.Start) == dt.Date).FirstOrDefault();
    return result != null;

}

上面的代码抛出以下错误:

    LINQ to Entities does not recognize the method 'System.Nullable`1[System.DateTime] TruncateTime(System.Nullable`1[System.DateTime])' method, and this method cannot be translated into a store expression.

我也尝试了以下代码,我得到了同样的错误:

var result = context.Games.Where(x => EntityFunctions.TruncateTime(x.Start) == EntityFunctions.TruncateTime(dt.Date)).FirstOrDefault();

我究竟做错了什么？

Answer 1

我最近在将我的Web应用程序从Entity Framework 5升级到Entity Framework 6时遇到了这个问题.然后,我意识到System.Data.Entity需要从应用程序中完全删除DLL才能使用Entity Framework 6.实体框架6不属于.NET Framework,因此它独立于System.Data.Entity dll.为了截断时间,您需要使用System.Data.Entity.DbFunctions.TruncateTime(...)EntityFramework.dll中的方法.是的,这解决了我的问题.

结论:如果您使用的是Entity Framework 6,请首先删除引用System.Data.EntityDLL,然后在代码中替换EntityFunctions.TruncateTime(..)为System.Data.Entity.DbFunctions.TruncateTime(...).[来自EntityFramework.dll]

Answer 2

我没有删除的参考System.Data.Entity,我刚从改变了通话DbFunctions.TruncateTime,以System.Data.Entity.DbFunctions.TruncateTime它为我工作.

我正在使用实体6.