Question

我有这个方法

Meeting是一个班级 Attendees是ICollection

中的Meeting

类

public partial class Meeting
    {

        public Meeting()
        {
            this.Attendees = new List<Attendees>();
        }

public virtual ICollection<Attendees> Attendees{ get; set; }
[...]

方法控制器

private void RemoveRowsDuplicated(Meeting model)
        {
            if (model.Attendees != null)
            {
                foreach (var item in model.Attendees.GroupBy(x => x.UserName).Select(y => y.Last()))
                {
                    context.Attendees.Remove(item);
                }
            }
        }

目标是删除表中具有相同用户名的重复参加者但是当前的方法是删除所有记录并保留副本
我哪里错了？

Answer 1

您的方法的正确版本将如下所示：

private static void RemoveRowsDuplicated(Meeting model)
        {
            if (model.Attendees != null)
            {
                var duplicates = new List<Attendees>();
                foreach (var item in model.Attendees.GroupBy(x => x.UserName).Where(x=>x.Count()>1))
                {
                    duplicates.AddRange(item.Skip(1));
                }
                duplicates.ForEach(x=>context.Attendees.Remove(x));
            }
        }

Answer 2

我可以看到你按名称分组元素并删除最后一项。所以你删除了独特的元素。喜欢这个

 private void RemoveRowsDuplicated(Meeting model)
        {
             if (model.Attendees != null)
             {
                var temporaryAtendees = new List<Attendees>();
                foreach(var item in model.Attendees)
                {
                    if (temporaryAtendees.Contains(item))
                    {
                        context.Attendees.Remove(item);
                    }
                    else
                    {
                        temporaryAtendees.Add(item);
                    }
                }
                }
            }

Answer 3

您可以尝试编写原始SQL并通过EF调用并返回列表中的Attendees对象。

var query = "Select * from Attendees group by username";
var attendeesList = dbContext.Database.SqlQuery<Attendees>(query).ToList<Attendees>();

删除重复的行mvc

3 个答案: