MongoDB 和 C# Find()

问题描述

我有以下代码，我是 mongodb 的新手，我需要帮助来查找集合中的特定元素.

I have the below code and I am new to mongodb, I need help in finding an specific element in the collection.

using MongoDB.Bson;
using MongoDB.Driver;
namespace mongo_console    {

public class User    {
    public ObjectId Id { get; set; }
    public string name { get; set; }
    public string pwd { get; set; }
}
class Program    {
    static void Main(string[] args)
    {
        MongoClient client = new MongoClient();
        MongoServer server = client.GetServer();
        MongoDatabase db = server.GetDatabase("Users");
        MongoCollection<User> collection = db.GetCollection<User>("users");

        User user = new User
        {
            Id = ObjectId.GenerateNewId(),
            name = "*****",
            pwd = "*****"
        };
        User user2 = new User
        {
            Id = ObjectId.GenerateNewId(),
            name = "system",
            pwd = "system"
        };
        collection.Save(user);
        collection.Save(user2);

        /*
         * How do I collection.Find() for example using the name
         */
  }
}
}

一旦我找到我想要打印的用户，这是可能的还是只会找到返回位置?如果是这样，我该如何打印?

Once I find the user I will like to print it, is that posible or will find only return the position? if so, how do I print it?

我看过一些示例 collection.Find(x => x.something) 但我不知道 x 是什么或意味着什么

I have seen some examples collection.Find(x => x.something) but I do not know what that x is or mean

推荐答案

要查找记录，您可以在 find 中使用 Lambda，例如:

To find a record you could use Lambda in find, for example:

var results = collection.Find(x => x.name == "system").ToList();

或者，您可以使用支持强类型 Lambda 或文本的构建器:

Alternatively you can use Builders which work with strongly typed Lambda or text:

var filter = Builders<User>.Filter.Eq(x => x.name, "system")

或

var filter = Builders<User>.Filter.Eq("name", "system")

然后像上面一样使用find

And then use find as above

// results will be a collection of your documents matching your filter criteria

// Sync syntax
var results = collection.Find(filter).ToList();

// Async syntax
var results = await collection.Find(filter).ToListAsync();