ef-core-2.1 - 使用 EF core 2.1 调用 DbFunction

Question

我尝试调用存储在我的数据库中的标量函数。这是我的代码:

public class PronosticDbContext : DbContext
{
    public PronosticDbContext(DbContextOptions<PronosticDbContext> options) : base(options)
    {

    }

    [DbFunction(FunctionName = "GetPlayerPointsForDay", Schema = "dbo")]
    public static int GetPlayerPointsForDay(int dayId, int userId) => throw new NotSupportedException();    
}

电话:

private IQueryable<PlayerRankingData> GetPlayerRanking(int? dayId)
{
    return Context.Days.Where(x => x.Id == dayId.Value).Select(x => new PlayerRankingData
    {
        // Some properties
        Users = x.Season.Users.Select(us => new PlayerRankingData.User
        {
            // Other properties
            Last = PronosticDbContext.GetPlayerPointsForDay(x.Id, us.User.Id),
            // Others again
        }).OrderByDescending(u => u.Points).ThenByDescending(u => u.Last).ThenBy(u => u.Login)
    });
}

我不明白为什么，但我总是转到 NotSupportedException，我的标量函数从未被调用。为什么我错过了？

我也这样试过，结果一样。

modelBuilder
    .HasDbFunction(typeof(PronosticDbContext).GetMethod(nameof(GetPlayerPointsForDay)))
    .HasSchema("dbo")
    .HasName(nameof(GetPlayerPointsForDay));

Answer 1

好的，我知道了。

问题是你不能直接调用标量函数(我不知道为什么)，它必须封装在一个 linq 查询中，像这样:

Last = Context.Users.Select(u => PronosticDbContext.GetPlayerPointsForDay(x.Id, us.User.Id)).FirstOrDefault()

仅此而已。无需在 DbContext 中声明，这就足够了:

[DbFunction]
public static int? GetPlayerPointsForDay(int dayId, int userId) => throw new NotSupportedException();