是这样的，我们有一个场景，另一个服务器是写到MongoDB里面，我们的MVC页面要展示，需要分页展示

自己写了一个DAL

public class MongoConnect
{
public string ConnectString { get; set; }
}

public class MongoBaseDAL<TEntity>  
{  
    public MongoBaseDAL(IOptions<MongoConnect> options)  
    {  
        ConnectString = options.Value.ConnectString;  
    }

    private string ConnectString { get; set; } = "192.168.50.110:27017";

    protected MongoClient Create()  
    {  
        var client = new MongoClient($"mongodb://{ConnectString}");  
        return client;  
    }

    protected IMongoDatabase GetDatabase(string database)  
    {  
        var client = Create();  
        var db = client.GetDatabase(database);

        return db;  
    }

    protected IMongoCollection<TEntity> CreateQuery(string database,string tableName)  
    {  
        var db = GetDatabase(database);  
        return db.GetCollection<TEntity>(tableName);  
    }

    protected PageDataView<TEntity> Page(string database, string tableName, Dictionary<string, BsonValue> dictionary, int pageSize, int currentPage)  
    {  
        var where = Builders<TEntity>.Filter.Empty;  
        if (dictionary.Count > )  
        {  
            var filterBuilder = Builders<TEntity>.Filter;

            List<FilterDefinition<TEntity>> listFilter = new List<FilterDefinition<TEntity>>();

            foreach (var pair in dictionary)  
            {  
                listFilter.Add(filterBuilder.Eq(pair.Key, pair.Value));  
            }

            where = filterBuilder.And(listFilter);  
        }

        PageDataView<TEntity> result = new PageDataView<TEntity>();

        var query = CreateQuery(database, tableName);  
        result.TotalRecords = (int)query.CountDocuments(where);  
        result.TotalPages = result.TotalRecords / pageSize;  
        if (result.TotalRecords % pageSize > )  
            result.TotalPages += ;

        var list = query.Find(where).Skip((currentPage - ) \* pageSize).Limit(pageSize).ToList();  
        result.Items = list;

        return result;  
    }  
}

比如有个类CreatedTableLog

那个Helper就是

public class CreatedTableLogHelper: MongoBaseDAL<CreatedTableLog>  
{  
    public static string Database = "Base";  
    public static string Table = "CreatedTableLog";

    public CreatedTableLogHelper(IOptions<MongoConnect> options) : base(options)  
    {  
    }

    public PageDataView<CreatedTableLog> GetListByPage(Dictionary<string, BsonValue> dictionary, int pageSize, int currentPage)  
    {  
        return Page(Database, Table, dictionary, pageSize, currentPage);  
    }  
}

在StartUp里面增加代码

        #region MongoDB  
        services.Configure<MongoConnect>(Configuration.GetSection("MongoConnect"));  
        services.AddScoped(typeof(MongoBaseDAL<>));  
        services.AddScoped<CreatedTableLogHelper>();  
        #endregion

打开配置文件

appsettings.Development.json这个是DEBUG版本的配置文件

写入配置

"MongoConnect": {
"ConnectString": "192.168.50.110:27017"
}

192.168.50.110是我测试环境是MongoDB服务器地址，端口默认

appsettings.Development.json这个是Release版本的配置文件可能这个地址就是localhost了，要对应更改

比如CreatedTableLog表有三个字段

UserId和NickName需要查询

        Dictionary<string, BsonValue> dictionary = new Dictionary<string, BsonValue>();

        var index = model.Start ==  ?  : (model.Start / model.Length) + ;

        if (model.UserId != )  
        {  
            dictionary.Add("UserId", BsonInt64.Create(model.UserId));  
        }

        if (!string.IsNullOrWhiteSpace(model.NickName))  
        {  
            dictionary.Add("NickName", BsonString.Create(model.NickName));  
        }

        var result = CreatedTableLogHelper.GetListByPage(dictionary, model.Length, index);

这样你以为就ok了？no no no

会报错的，为什么同一个实体model，写入正常，读会报错_id错误呢？

因为实体model如果没有Id类型是ObjectId，会自动构建，但是你反序列化就会错误了

增加一个继承类

public class MongoDbBase  
{  
    private ObjectId \_id;  
    public ObjectId Id  
    {  
        get { return \_id; }  
        set { \_id = value; }  
    }  
}

你需要反序列化的实体对象继承

比如CreatedTableLog改为

public class CreatedTableLog: MongoDbBase

再读一下，对了吧？大功告成