如何在C＃中使用Mongo的Aggregate框架在列表字段中累积项目？

问题描述

我有以下实体：

public class MyEntity {
    public string Id { get; set; }
    public string Code { get; set; }
    public decimal Amount { get; set; }
}

public class MyPageItem {
    public string Code { get; set; }
    public decimal Total { get; set; }
    public IList<string> Ids { get; set; } = new List<string>{};
}

以及以下分组：

IMongoCollection<MyEntity> myCollection = MongoClient.GetDatabase("DatabaseName").GetCollection<MyEntity>("MyEntity");
    
myCollection.Aggregate()
                .sort(new SortDeFinitionBuilder<MyEntity>().Ascending("code"))
                .Group(
                        x => x.Code,g => new MyPageItem {
                            Code = g.Select(x => x.Code).Last(),Total = g.Select(x => x.Amount).Sum(),Ids = //how to append Ids in this field?
                        }
                    )
                .ToListAsync();

我想在List<string> Ids中添加所有ID。我该怎么办？

解决方法

反序列化查询时，使用IList界面会导致错误，但是您可以切换到：

public List<string> Ids { get; set; }

然后使用：

collection.Aggregate()
            .Group(
                x => x.Code,gr => new MyPageItem()
                {
                    Code = gr.Key,Total = gr.Sum(x => x.Amount),Ids = gr.Select(y => y.Id).ToList()
                }
            )