MongoDB在CSharp里实现Aggregate

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今天主要用了一个 mongodb.driver 里的分组，事实上在网上介绍这方面的文章非常少，以至于我在出现问题后，无法找到一个正确的解决方案，最后还是通过异常信息找到的解决方法，所以感觉自己更应该去写一篇关于如何在C#驱动里进行聚合 Aggregate 的文章！

/// <summary>
/// 返回 UI 消息树
/// </summary>
/// <returns></returns>
public static string GetMongoLog(DateTime? fromDate, DateTime? toDate, int page = 1)
{
string from = DateTime.Now.Date.ToString(“yyyy-MM-dd”);
string to = DateTime.Now.Date.AddDays(1).ToString(“yyyy-MM-dd”);
if (fromDate.HasValue)
{
from = fromDate.Value.ToString(“yyyy-MM-dd”);

}
if (toDate.HasValue)
{
to = toDate.Value.ToString(“yyyy-MM-dd”);
}
var stages = new List<IPipelineStageDefinition>();
stages.Add(new JsonPipelineStageDefinition<BsonDocument, BsonDocument>(“{$match:{AddTime:{$gt:ISODate(‘” + from + “‘),$lt:ISODate(‘” + to + “‘)}}}”));
stages.Add(new JsonPipelineStageDefinition<BsonDocument, BsonDocument>(“{$group:{_id: \”$RootId\”, count: {$sum: 1}}}”));
stages.Add(new JsonPipelineStageDefinition<BsonDocument, BsonDocument>(“{$skip:” + page * 5 + “}”));
stages.Add(new JsonPipelineStageDefinition<BsonDocument, BsonDocument>(“{$limit:5}”));
var pipeline = new PipelineStagePipelineDefinition<BsonDocument, BsonDocument>(stages);
var result = NoSql.MongodbManager<LoggerContext>.Collection.Aggregate(pipeline);
StringBuilder str = new StringBuilder();

str.Append(“<ol class=’treeMsg’>”);
foreach (var item in result.ToList())
{
var timer = new List<DateTime>();
var old = NoSql.MongodbManager<LoggerContext>.Instance.Find(i => i.RootId == item.Values.ToArray()[0].ToString() && i.ParentId == null).FirstOrDefault();
timer.Add(old.AddTime);
str.Append(“<li style=’margin:5px;border:1px dashed #aaa’>”);
str.AppendFormat(“{0}{1}{2}”
, old.Url
, old.MessageBody
, old.AddTime);
MsgTree(str, old.ChildId, timer);
str.AppendFormat(“ 本次请求用时 {0} 毫秒（{1}秒）”
, (timer.Max() – timer.Min()).TotalMilliseconds
, (timer.Max() – timer.Min()).TotalSeconds);
str.Append(“</li>”);
}
str.Append(“</ol>”);
return str.ToString();
}