原始数据是这样的
{
"_id" : ObjectId("57b532aefc19a526b4cf7118"),
"_t" : [
"Product",
"ShoppingProduct"
],
"name" : "nike jug",
"createdByUser" : "",
"updatedAt" : ISODate("2016-08-18T03:59:42.012Z"),
"url" : "https://localhost:44305/v1/product/1",
"description" : "a jug from nike",
"schema" : "ShoppingProduct",
"sku" : "nikejug001",
"price" : "15",
"weight" : "100",
"brand" : null,
"manufacturerId" : ObjectId("000000000000000000000000"),
"entityId" : 1,
"visibility" : 4,
"status" : 1,
"taxClassId" : 2,
"shortDescription" : "nike jug is good"
}
这是我做的
var result = _col.Find("{}").Project("{entityId:1}").ToList();
希望返回数据是这样的
{
"_id" : ObjectId("57b532aefc19a526b4cf7118"),
"entityId" : 1
}
但我得到的是:
{
"name": "_id",
"value": "57b532aefc19a526b4cf7118"
},
{
"name": "entityId",
"value": 1
}
如何使用 C# 驱动程序实现类似 db.getCollection('products').find({},{entityId:1})
的功能?
最佳答案
这是正常行为。查询Return the Specified Fields and the _id Field Only对比Return Specified Fields Only在官方文档中。
var empty = Builders<BsonDocument>.Filter.Empty;
var docs = _col.Find(empty).Project("{_id:0, entityId:1}").ToList();
foreach (var doc in docs)
{
if (doc.AsBsonDocument.ElementCount != 1)
throw new Exception("Should have only entityId fields");
}
docs = _col.Find(empty).Project("{entityId:1}").ToList();
foreach (var doc in docs)
{
if (doc.AsBsonDocument.ElementCount != 2)
throw new Exception("Should have _id and entityId fields");
}
关于c# - MongoDb C# 驱动程序投影返回名称和值对,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/39010417/