我无法找到正确的语法来替换嵌套在集合中的多个级别的对象数组。我的偏好是只更新单个属性,但由于阅读了下面的链接,似乎替换整个数组是最好的选择。
https://jira.mongodb.org/browse/SERVER-831
所以我有以下类作为例子:
public class Parent
{
public ObjectId _id { get; set; }
public string Firstname { get; set; }
public string Lastname { get; set; }
public Collection<Child> Children { get; set; }
}
public class Child
{
public ObjectId _id { get; set; }
public string Firstname { get; set; }
public string Lastname { get; set; }
public Collection<Pet> Pets { get; set; }
}
public class Pet
{
public string Name { get; set; }
}
使用以下代码,我创建了一个 Parent,添加了一些 Children,并将 Pet 添加到其中一个孩子。
// Construct Objects
Parent parent = new Parent() { _id = new ObjectId("4f979621682dbc1a8cefecb1") };
Collection<Child> children = new Collection<Child>();
Collection<Pet> pets = new Collection<Pet>();
children.Add(new Child()
{ _id = new ObjectId("4f979621682dbc1a8cefecaf"),
Firstname = "Child",
Lastname = "One" });
children.Add(new Child()
{ _id = new ObjectId("4f979621682dbc1a8cefecb0"),
Firstname = "Child",
Lastname = "Two" });
pets.Add(new Pet() { Name = "Fishy" });
parent.Children = children;
parent.Children[0].Pets = pets;
// Connect to Mongo
var server = MongoServer.Create("mongodb://localhost/?safe=true");
var db = server.GetDatabase("test");
// Insert into parent collection
MongoCollection<Parent> parents;
parents = db.GetCollection<Parent>("parents");
parents.Insert<Parent>(parent, MongoDB.Driver.SafeMode.True);
这成功插入对象,生成以下 JSON 结果:
{ "_id" : ObjectId("4f979621682dbc1a8cefecb1"),
"Firstname" : null,
"Lastname" : null,
"Children" :
[
{
"_id" : ObjectId("4f979621682dbc1a8cefecaf"),
"Firstname" : "Child",
"Lastname" : "One",
"Pets" :
[
{
"Name" : "Fishy"
}
]
},
{
"_id" : ObjectId("4f979621682dbc1a8cefecb0"),
"Firstname" : "Child",
"Lastname" : "Two",
"Pets" : null
}
]
}
更新单个文档元素似乎也是一个微不足道的过程,并且可以使用以下代码成功运行。
// Change children's name
var query = new QueryDocument { { "Children._id", new ObjectId("4f979621682dbc1a8cefecaf") } };
var update = Update.Set("Children.$.Firstname", "Something");
parents.Update(query, update);
现在我无法解决的问题是如何替换 Pets 数组。以下代码无法编译,因为 Update.Set 不接受集合。
// Change pets information
pets[0].Name = "Fishy2"; // change to pet
pets.Add(new Pet() { Name = "Doggy" }); // add new pet
query = new QueryDocument { { "Children._id", new ObjectId("4f979621682dbc1a8cefecaf") } };
update = Update.Set("Children.$.Pets", pets);
parents.Update(query, update);
那么,让我能够更新 Pets 数组中的详细信息的最佳过程是什么?