[英]How to fetch collection of subdocument using mongodb C# driver?
I have following MongoDB document:我有以下 MongoDB 文档:
{
"_id": {
"$oid": "5fbfa0005c15aaf2eac69ba6"
},
"PostMedia": [
{
"FilePath": "http://localhost:8886/localhost44323/image/",
"Filename": "img1.jpg",
"Title": null,
"Description": ""
},
{
"FilePath": "http://localhost:8886/localhost44323/image/",
"Filename": "img2.jpg",
"Title": null,
"Description": ""
}
]
},
{
"_id": {
"$oid": "5fbfa0485c15aaf2eac69ba7"
},
"PostMedia": [
{
"FilePath": "http://localhost:8886/localhost44323/image/",
"Filename": "img3.jpg",
"Title": null,
"Description": ""
},
{
"FilePath": "http://localhost:8886/localhost44323/image/",
"Filename": "img4.jpg",
"Title": null,
"Description": ""
}
]
}
and I want to fetch all PostMedia
to single array using MongoDB C# driver.我想使用 MongoDB C# 驱动程序将所有PostMedia
获取到单个数组。 Here is the expected result:这是预期的结果:
[
{
"FilePath": "http://localhost:8886/localhost44323/image/",
"Filename": "img1.jpg",
"Title": null,
"Description": ""
},
{
"FilePath": "http://localhost:8886/localhost44323/image/",
"Filename": "img2.jpg",
"Title": null,
"Description": ""
}, {
"FilePath": "http://localhost:8886/localhost44323/image/",
"Filename": "img3.jpg",
"Title": null,
"Description": ""
},
{
"FilePath": "http://localhost:8886/localhost44323/image/",
"Filename": "img4.jpg",
"Title": null,
"Description": ""
}
]
I had tried to use group aggregation function but it returned an array of array.我曾尝试使用组聚合 function 但它返回了一个数组数组。
Result I received:我收到的结果:
PostMedia:[{
"FilePath": "http://localhost:8886/localhost44323/image/",
"Filename": "img1.jpg",
"Title": null,
"Description": ""
},
{
"FilePath": "http://localhost:8886/localhost44323/image/",
"Filename": "img2.jpg",
"Title": null,
"Description": ""
}],[
{
"FilePath": "http://localhost:8886/localhost44323/image/",
"Filename": "img3.jpg",
"Title": null,
"Description": ""
},
{
"FilePath": "http://localhost:8886/localhost44323/image/",
"Filename": "img4.jpg",
"Title": null,
"Description": ""
}
]
C# code I have written so far is as follows:目前我写的C#代码如下:
var group = new[]
{
new BsonDocument("$group",
new BsonDocument
{
{ "_id", BsonNull.Value },
{ "PostMedia", new BsonDocument("$push", "$PostMedia") }
})
};
var result = collection.Aggregate<MediaList>(group).FirstOrDefault();
return list;
}
Is there any way to fetch subdocument by merging them is a single array.有没有办法通过合并它们来获取子文档是一个数组。
You have to $unwind
before $group
,您必须在$group
之前 $ $unwind
,
$unwind
deconstruct PostMedia
array $unwind
解构PostMedia
数组$replaceRoot
replace PostMedia
object to root $replaceRoot
将PostMedia
object 替换为 root$unset
remove _id
field $unset
删除_id
字段 { $unwind: "$PostMedia" },
{
$group: {
_id: null,
PostMedia: { $push: "$PostMedia" }
}
},
{ $unset: "_id" } // remove field
C#: C#:
new BsonArray
{
new BsonDocument("$unwind", "$PostMedia"),
new BsonDocument("$group",
new BsonDocument
{
{ "_id", BsonNull.Value },
{ "PostMedia",
new BsonDocument("$push", "$PostMedia") }
})
new BsonDocument("$unset", "_id")
}
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