Question

我正在将C＃8，.net标准2.0与MongoDB.Driver v2.9.2一起使用。我正在将一个项目从RavenDB迁移到MongoDB。

我需要在我的GetAllAsync方法中对IMongoQueryable使用 include ，但我感到困惑。这是方法；

public async Task<ICollection<TEntity>> GetAllAsync<TOrderBy>(Expression<Func<TEntity, TOrderBy>> orderBy, 
                               bool isDescendingOrder = false, 
                               Expression<Func<TEntity, object>> projection = null,
                               CancellationToken cancellationToken = default)
        {
            IMongoQueryable<TEntity> mongoQueryable = Collection.AsQueryable();

            if (isDescendingOrder)
            {
                return await mongoQueryable.OrderByDescending(orderBy)
                                           .ToListAsync(cancellationToken: cancellationToken);
            }

            return await mongoQueryable.OrderBy(orderBy)
                                       .ToListAsync(cancellationToken: cancellationToken);
        }

到目前为止我尝试过的我可以使用“ Find（）”方法构建相同的查询，但是 SortByDescending方法需要“ Expression<Func<TEntity, object>> orderBy”-不能与Expression<Func<TEntity, TOrderBy>> orderBy一起使用，就像我提供的上层代码块一样。

Builders<TEntity>.Sort.Ascending(orderBy).

Func<TEntity, TOrderBy> compile = orderBy.Compile();
Collection.Find(new BsonDocument()).Project(projection).SortByDescending(compile).ToListAsync();

最后一件事，这就是我如何在RavenDB中解决此问题：

public async Task<ICollection<TEntity>> GetAllAsync<TOrderBy>(Expression<Func<TEntity, TOrderBy>> orderBy, 
                                       bool isDescendingOrder = false, 
                                       Expression<Func<TEntity, object>> projection = null,
                                       CancellationToken cancellationToken = default)
        {
            ICollection<TEntity> entities;

            IRavenQueryable<TEntity> query = AsyncDocumentSession.Query<TEntity>();

            if (projection != null)
            {
                query = query.Include(projection);
            }

            if (isDescendingOrder)
            {
                entities = await query.OrderByDescending(orderBy)
                                      .ToListAsync(token: cancellationToken);
            }
            else
            {
                entities = await query.OrderBy(orderBy)
                                      .ToListAsync(token: cancellationToken);
            }

            return entities;
        }

Answer 1

尝试以下操作：

BindingSources

测试程序：

ComboBoxes

如何在C＃中将Iq投影与IMongoQueryable <TEntity>一起使用

1 个答案: