"_id" : "639d8a50-7864-458f-9a7d-b72647a3d226",
"ParentGuid" : "00000000-0000-0000-0000-000000000000",
"Name" : "汉字",
"Describe" : "",
"Enable" : true,
"Level" : 2,
"Subject" : "语文",
"Exams" : [
{
"ExamGuid" : "6635e1c6-2a22-404e-b58c-97ed9fc49ffc",
"Grade" : "G2",
"Questions" : [
{
"_id" : "97eeeaaa-5902-4c11-bcdb-8b7a70485753"
},
{
"_id" : "628d5613-90b1-44fa-b02d-4074e86aa751"
}
]
},
{
"ExamGuid" : "b1e72692-6b63-4d98-a4bb-1b48765e7a96",
"Grade" : "G1",
"Questions" : [
{
"_id" : "628d5613-90b1-44fa-b02d-4074e86aa751"
}
]
}
]
场景1：给内嵌集合的元素添加一个新的元素
1.首先根据筛选条件确定元素
var filter = Builders<CustomKnowPoint>.Filter.And(
Builders<CustomKnowPoint>.Filter.Eq(o => o.Id, "639d8a50-7864-458f-9a7d-b72647a3d226"),
Builders<CustomKnowPoint>.Filter.Eq("Exams.ExamGuid", "6635e1c6-2a22-404e-b58c-97ed9fc49ffc"));
CustomKnowPoint为MongoDB映射的对象 Builders<CustomKnowPoint>.Filter.And 方法的参数是一个param[]数组,意思是将所有的过滤条件用And且的关系合并
var update = Builders<CustomKnowPoint>.Update.Push("Exams.$.Questions", new QuestionGuid(Guid.NewGuid().ToString()));this.Collection.FindOneAndUpdate(filter, update);
2.执行后Questions内嵌集合就会在元素的末尾添加一条新的记录
场景2：内嵌集合的元素进行删除
过滤条件同上面的新增一样 通过对象本身的Id和内嵌元素的ExamGuid固定内嵌文档,移除文档的具体Filter对象是移除对象本身Builders<QuestionGuid>.Filter而不是Builders<CustomKnowPoint>.Filter
var update = Builders<CustomKnowPoint>.Update.PullFilter("Exams.$.Questions", Builders<QuestionGuid>.Filter.Eq("_id", "628d5613-90b1-44fa-b02d-4074e86aa751"));this.Collection.FindOneAndUpdate(filter, update);
场景3：聚合使用
MongoDB的聚合管道将MongoDB文档在一个管道处理完毕后将结果传递给下一个管道处理。管道操作是可以重复的。表达式：处理输入文档并输出。表达式是无状态的，只能用于计算当前聚合管道的文档，不能处理其它的文档。
"_id" : "639d8a50-7864-458f-9a7d-b72647a3d226",
"ParentGuid" : "00000000-0000-0000-0000-000000000000",
"Name" : "汉字",
"Describe" : "",
"Enable" : true,
"Level" : ,
"Subject" : "语文",
"Exams" : [
{
"ExamGuid" : "6635e1c6-2a22-404e-b58c-97ed9fc49ffc",
"Grade" : "G2",
"Questions" : [
{
"_id" : "97eeeaaa-5902-4c11-bcdb-8b7a70485753"
},
{
"_id" : "628d5613-90b1-44fa-b02d-4074e86aa751"
}
]
}
]
当我们只需要返回内嵌文档部分的时候 这种场景下我们就可以用到聚合来操作了 执行MongoDB语句
db.KnowPoint.aggregate(
[
{
/*此处$unwind：将文档中的某一个数组类型字段拆分成多条，每条包含数组中的一个值。*/
$unwind : "$Exams"
},
{
/*此处$match ：过滤文档筛选条件。*/
$match :
{
"Exams.ExamGuid" : "6635e1c6-2a22-404e-b58c-97ed9fc49ffc"
}
},
{
/*此处group 分组。*/
$group :
{
_id :
{
/*此处按照各种属性拼凑分组 将各属性组成一个Id的属性*/
"_id" : "$_id", "ParentGuid" : "$ParentGuid", "Name" : "$Name", "Enable" : "$Enable", "Level" : "$Level", "Subject" : "$Subject"
},
"Exams" :
{
/*此处push将之前分组的Exams再写进去*/
"$push" : "$Exams"
}
}
}
])
相应的C# 驱动程序
List<string> keys = new List<string>() { "_id", "ParentGuid", "Name", "Enable", "Level", "Subject" };
var stages = new List<IPipelineStageDefinition>();
#region 过滤条件
stages.Add(new JsonPipelineStageDefinition<BsonDocument, BsonDocument>
(
"{" +
"$unwind:\"$Exams\"" +
"}"
));
stages.Add(new JsonPipelineStageDefinition<BsonDocument, BsonDocument>
(
"{" +
"$match:" +
"{" +
"\"Exams.ExamGuid\":" +
"{" +
"$in:" + JsonConvert.SerializeObject(new List<string>() { "6635e1c6-2a22-404e-b58c-97ed9fc49ffc"}) +
"}" +
"}" +
"}"
));
stages.Add(new JsonPipelineStageDefinition<BsonDocument, BsonDocument>
(
"{" +
"$group:" +
"{" +
"_id:{ " + string.Join(",", keys.Select(o => "\"" + o + "\":\"$" + o + "\"").ToList()) + " }," +
"Exams:{$push:\"$Exams\"}" +
"}" +
"}"
));
#endregion
var pipeline = new PipelineStagePipelineDefinition<BsonDocument, BsonDocument>(stages);
var result = this.Context
.DbSet<BsonDocument>(nameof(KnowPoint))
.Aggregate(pipeline)
.ToList()