如何在MongoDB C#驱动程序版本2中使用$位置运算符

问题描述

我需要更新文档的数组子文档中一个元素的字段.

I need to update a field of one element from array sub document of a document.

MongoDB具有$位置运算符来执行此操作.但是在MongoDB C#驱动程序版本2中，似乎不支持此运算符.

MongoDB have the $ positional operator to do this. But in MongoDB C# driver version 2 it seems that there is no support for this operator.

我该如何实现?

文档:

{ "_id" : 1, "grades" : [ 80, 85, 90 ] }
{ "_id" : 2, "grades" : [ 88, 90, 92 ] }
{ "_id" : 3, "grades" : [ 85, 100, 90 ] }

预期查询:

db.students.update(
     { _id: 1, grades: 80 },
     { $set: { "grades.$" : 82 } }
   )

推荐答案

您可以尝试类似的方法.

You can try something like this.

var builder = Builders<Student>.Filter;
var filter = builder.Eq(student=> student.Id, 1) & builder.ElemMatch(student => student.Grades, x => x == 80);

var builder = Builders<Student>.Update;
var update = builder.Set(student => student.Grades[-1], 82);

var result = collection.UpdateOne(filter, update);

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