c# - Entity Framework Core 中 TimeSpan 的总和

Question

我有一个 View 模型用于在索引页上显示我的类(class)

public class ShowCourseListItemViewModel
{
    public int CourseId { get; set; }
    public string Title { get; set; }
    public string ImageName { get; set; }
    public int Price { get; set; }
    public TimeSpan TotalTime { get; set; }
}

我有获取所有类(class)的服务:

...
return result.Include(e => e.CourseEpisodes).Select(c => new ShowCourseListItemViewModel()
{
    CourseId = c.CourseId,
    Title = c.CourseTitle,
    ImageName = c.CourseImageName,
    Price = c.CoursePrice,
    TotalTime = new TimeSpan(c.CourseEpisodes.Sum(e => e.EpisodeTime.Ticks)) <== Error is Here
}).Skip(skip).Take(take).ToList();
...

错误文本:

An unhandled exception occurred while processing the request. InvalidOperationException: The LINQ expression 'DbSet() .Where(c0 => EF.Property<Nullable>(EntityShaperExpression: EntityType: Course ValueBufferExpression: ProjectionBindingExpression: EmptyProjectionMember IsNullable: False , "CourseId") != null && object.Equals( objA: (object)EF.Property<Nullable>(EntityShaperExpression: EntityType: Course ValueBufferExpression: ProjectionBindingExpression: EmptyProjectionMember IsNullable: False , "CourseId"), objB: (object)EF.Property<Nullable>(c0, "CourseId"))) .Sum(c0 => c0.EpisodeTime.Ticks)' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'. See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.

我认为问题是 TimeSpan 的总和。对这个总结有什么建议吗？

Answer 1

        return result.Include(e => e.CourseEpisodes).AsEnumerable()
            .Select(c => new ShowCourseListItemViewModel()
            {
                CourseId = c.CourseId,
                Title = c.CourseTitle,
                ImageName = c.CourseImageName,
                Price = c.CoursePrice,
                TotalTime = new TimeSpan(c.CourseEpisodes.ToList().Sum(e => e.EpisodeTime.Ticks))
            }).Skip(skip).Take(take).ToList();