c# MongoDB分页辅助类，支持多条件查询

创建一个获取MongoDB数据库实例的类

    public class Db

    {

        private static IMongoDatabase db = null;

        private static readonly object lockHelper = new object();

        private Db() { }

        public static IMongoDatabase GetDb(string connStr, string dbName)

        {

            if (db == null)

            {

                lock (lockHelper)

                {

                    if (db == null)

                    {

                        var client = new MongoClient(connStr);

                        db = client.GetDatabase(dbName);

                    }

                }

            }

            return db;

        }

    }

创建一个操作MongDB的辅助类

    public class MongoDbHelper<T> where T : MongoBaseEntity, new()

    {

        private IMongoDatabase db = null;

        private IMongoCollection<T> collection = null;

        private readonly IOptions<MongoDBConfig> _options;

        public MongoDbHelper(IOptions<MongoDBConfig> options)

        {

            this._options = options;

            this.db = Db.GetDb(this._options.Value.ConnectionString, this._options.Value.DbName);

            this.collection = db.GetCollection<T>(typeof(T).Name);

        }

        /// <summary>

        /// 分页

        /// </summary>

        /// <param name="filter"></param>

        /// <param name="sort"></param>

        /// <param name="pageIndex"></param>

        /// <param name="pageSize"></param>

        /// <returns></returns>

        public PagingModel<T> GetPagingData(FilterDefinition<T> filter, SortDefinition<T> sort, int pageIndex, int pageSize)

        {

            var list = this.collection

                .Find(filter)

                .Sort(sort)

                .Skip((pageIndex - ) * pageSize)

                .Limit(pageSize)

                .ToList();

            var count = this.collection.CountDocuments(filter);

            var pagingModel = new PagingModel<T>();

            pagingModel.Items = list;

            pagingModel.PageIndex = pageIndex;

            pagingModel.PageSize = pageSize;

            pagingModel.TotalRecords = Convert.ToInt32(count);

            pagingModel.TotalPages = (int)Math.Ceiling((double)count / (double)pageSize);

            return pagingModel;

        }

    }

说明：构造方法public MongoDbHelper(IOptions<MongoDBConfig> options)中的参数，是与配置文件中的MongoDBConfig节点对应的，我的项目是.net core项目。

下面是appsettings.json配置文件部分代码：

  "MongoDBConfig": {

    "ConnectionString": "mongodb://xxx:xxx@192.168.3.240:27017",

    "DbName": "xxxDB"

  }

    public class MongoDBConfig

    {

        /// <summary>

        /// 数据库连接字符串

        /// </summary>

        public string ConnectionString { get; set; }

        /// <summary>

        /// 具体数据库名称

        /// </summary>

        public string DbName { get; set; }

    }

创建一个分页实体类

    /// <summary>

    /// 描述：分页实体

    /// 创建人：苏本东

    /// 创建时间：2019-3-5 19:05:20

    /// </summary>

    /// <typeparam name="T"></typeparam>

    public class PagingModel<T> where T : class, new()

    {

        /// <summary>

        /// 当前页码

        /// </summary>

        public int PageIndex { get; set; }

        /// <summary>

        /// 每页大小

        /// </summary>

        public int PageSize { get; set; }

        /// <summary>

        /// 总记录数

        /// </summary>

        public int TotalRecords { get; set; }

        /// <summary>

        /// 总页数

        /// </summary>

        public int TotalPages { get; set; }

        /// <summary>

        /// 每页数据

        /// </summary>

        public List<T> Items { get; set; }

    }

最后就是调用了

            FilterDefinition<ModbusData> filter = Builders<ModbusData>.Filter.Empty;

            if (request.Ip.IsNotNullAndEmpty())

            {

                //注意：Eq方法的第一个参数，大小写需要跟数据库一致，不然查询无效

                filter = Builders<ModbusData>.Filter.Eq("IP", request.Ip);

            }

            var sort = Builders<ModbusData>.Sort.Descending(c => c._id);

            var pagingModel = this._mongo.GetPagingData(filter,

                sort,

                (int)request.page,

                (int)request.limit);

ModbusData类是与MongoDB的表对应的

提供两篇文章供学习参考：

https://www.cnblogs.com/quebra/p/10202449.html

https://www.cnblogs.com/woxpp/p/6347429.html