Question

通过一些早期的帮助，我在SSIS中创建了一个C＃脚本，用于从MongoDB到SQL Server检索数据。虽然可以轻松检索常规文档，但嵌套文档和数组存在问题。

问题1 ：我有shipping_address.country，使用

返回结果

this.UserDBBuffer.SCountry = document["shipping_address"].AsBsonDocument["country"].ToString();

然而， mlocation.address 给我一个错误'“country”找不到'使用相同的代码：

this.UserDBBuffer.Country = document["mlocation"].AsBsonDocument["country"].ToString();

问题2 ：从数组中检索项目。我有一个看起来像“设备 - ＆gt;文档 - ＆gt; device_data - ＆gt;模型”或“设备 - ＆gt;文档 - ＆gt; device_data - ＆gt;品牌”的数组。如何在代码中检索“模型”或“品牌”值？

非常感谢你的帮助。以下是我的全部代码：

public override void CreateNewOutputRows()
{
    string connectionString = "mongodb://localhost";
    MongoServer myMongo = MongoServer.Create(connectionString);
    myMongo.Connect();
    var db = myMongo.GetDatabase("UserDB");

    //Declaring variables for Date Created conversions
    string DateCreatedString;
    DateTime DateCreatedDateUTC;
    DateTime DateCreatedDateLocal;

    var fields = Fields.Include("mlocation.country", "mlocation", "_id", "primary_email", "gender", "date_created");
    var collection = db.GetCollection<BsonDocument>("users");

    foreach (var document in collection.FindAll().SetFields(fields))
    {
        this.UserDBBuffer.AddRow();
        this.UserDBBuffer.ID = document["_id"] == null ? "" : document["_id"].ToString();
        this.UserDBBuffer.Country = document["mlocation"].AsBsonDocument["country"].ToString();
        this.UserDBBuffer.PrimaryEmail = document["primary_email"] == null ? "" : document["primary_email"].ToString();
        this.UserDBBuffer.Gender = document["gender"] == null ? "" : document["gender"].ToString();

        //Importing Date Created as String for data manipulation
        DateCreatedString = document["date_created"] == null ? "" : document["date_created"].ToString();
        //First, making sure that we have a UTC datetime
        DateCreatedDateUTC = DateTime.Parse(DateCreatedString).ToUniversalTime();

        //Second, converting to Local Time
        DateCreatedDateLocal = DateTime.Parse(DateCreatedString).ToLocalTime();

        //Finally, assigning variables to rows
        this.UserDBBuffer.DateTimeCreatedUTC = DateCreatedDateUTC;
        this.UserDBBuffer.DateTimeCreatedLocal = DateCreatedDateLocal;
    }

    myMongo.Disconnect();
}

对于问题2，我找到了某人使用的Java脚本;如果我可以将它转换为C＃，它可能会有很大帮助：

count = 0;

function user_list(){
    var cursor = db.users.find()

    //var cursor = db.users.find({"devices": {"$ne":[]}})
    cursor.forEach(function(user) {
        var deviceInfo = "";
        if (user.devices){
            if (user.devices[0]){
                dd = user.devices[0].device_data; 
                if (dd) {
                    deviceInfo = dd.model + "," + dd.brand  + "," + dd.model + "," + dd.device + "," + dd.pixel_height + "," + dd.pixel_width + "," + dd.pixel_format;
                }
            }
        }
        var location = "";
        if (user.mlocation) location = user.mlocation.country;
        print(user._id + "," + location + "," + user.primary_email + "," + user.date_created + "," + deviceInfo);
        count++;
    });
}
user_list();
print(count);

Answer 1

对于问题1，您确定所有文档都包含字段位置，该字段位置是包含国家/地区字段的文档。我能够重现未找到的＆＃34; Element国家＆＃34;使用缺少值的文档。例如与

db.users.find（） {＆＃34; _id＆＃34; ：ObjectId（＆＃34; 4f04c56a0f8fa4413bed1078＆＃34;），＆＃34; primary_email＆＃34; ：＆＃34; email@email.com"，＆＃34; shipping_address＆＃34; ：[{＆＃34; country＆＃34; ：＆＃34; USA＆＃34;，＆＃34; city＆＃34; ：＆＃34;旧金山＆＃34; }，{＆＃34; country＆＃34; ：＆＃34; IN＆＃34;，＆＃34; city＆＃34; ：＆＃34; Chennai＆＃34; }，＆＃34; mlocation＆＃34; ：{＆＃34; country＆＃34; ：＆＃34;加拿大＆＃34;，＆＃34;城市＆＃34; ：＆＃34;蒙特利尔＆＃34; }} {＆＃34; _id＆＃34; ：ObjectId（＆＃34; 4f04d1605ab5a3805aaa8666＆＃34;），＆＃34; primary_email＆＃34; ：＆＃34; incorrect@email.com" ;,＆＃34; shipping_address＆＃34; ：[{＆＃34; country＆＃34; ：＆＃34; MX＆＃34;，＆＃34; city＆＃34; ：＆＃34;卡波圣卢卡斯＆＃34; }，＆＃34; mlocation＆＃34; ：{＆＃34; city＆＃34; ：＆＃34;蒙特利尔＆＃34; }} 第二个文件抛出异常。您可以检查其存在还是使用默认值选项文件[＆＃34; mlocation＆＃34;]。AsBsonDocument.GetValue（＆＃34; country＆＃34;，null）

对于问题2，您不能将BsonArray强制转换为文档。所以对于上面的例子来获取shipping_address.country你可以做类似

的事情

foreach (var addr in document["shipping_address"].AsBsonArray)
{
    var country = addr.AsBsonDocument["country"].AsString;
}

Answer 2

假设devices元素是一个数组，只需向下钻取到您要查找的元素，如下所示：

BsonDocument document; // assume this comes from somewhere
var devices = document["devices"].AsBsonArray;
var device = devices[0].AsBsonDocument; // first element of array
var deviceData = device["device_data"].AsBsonDocument;
var model = deviceData["model"].AsString;
var brand = deviceData["brand"].AsString;

为了清楚起见，我已将其细分为步骤，但如果您愿意，可以将其中一些步骤合并为更长的语句。

Answer 3

为了澄清您对Robert的回答的评论，您可以使用BsonDocument.Contains检查给定的BsonDocument是否包含指定名称的字段，然后再获取其值（http://api.mongodb.org/csharp/current/html /6181f23f-f6ce-fc7d-25a7-fc682ffd3c04.htm）

Answer 4

而不是：

var mlocation = document["mlocation"].AsBsonDocument;
var country = "";
if (mlocation != null && mlocation.Contains("country"))
{
    country = mlocation.AsBsonDocument.GetValue("country").ToString();
}

我会写：

var mlocation = document["mlocation"].AsBsonDocument;
var country = "";
if (mlocation.Contains("country"))
{
    country = mlocation["country"].AsString;
}

而不是：

var devices = document["devices"].AsBsonArray;
if (devices.ToList().Count > 0)
{
    if (devices[0].AsBsonDocument != null)
    {
        var deviceinfo = devices[0].AsBsonDocument;
        if (deviceinfo["device_data"].AsBsonDocument != null)
        {
            var deviceData = deviceinfo["device_data"].AsBsonDocument;
            model = deviceData.GetValue("model", null).AsString;
        }
    }
}

我会写：

var devices = document["devices"].AsBsonArray;
if (devices.Count > 0)
{
    var deviceinfo = devices[0].AsBsonDocument;
    if (deviceinfo.Contains("device_data"))
    {
        var deviceData = deviceinfo["device_data"].AsBsonDocument;
        var model = deviceData.GetValue("model", "").AsString; // "" instead of null
    }
}

查询MongoDB中的嵌套对象（第2部分）

4 个答案: