c# MongoDB分頁輔助類，支持多條件查詢

創建一個獲取MongoDB數據庫實例的類

    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;
        }
    }

創建一個操作MongDB的輔助類

    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>
        /// 分頁
        /// </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 - 1) * 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;
        }
    }

說明：構造方法public MongoDbHelper(IOptions<MongoDBConfig> options)中的參數，是與配置文件中的MongoDBConfig節點對應的，我的項目是.net core項目。 

下面是appsettings.json配置文件部分代碼：

  "MongoDBConfig": {
    "ConnectionString": "mongodb://xxx:xxx@192.168.3.240:27017",
    "DbName": "xxxDB"
  }

    public class MongoDBConfig
    {
        /// <summary>
        /// 數據庫連接字符串
        /// </summary>
        public string ConnectionString { get; set; }

        /// <summary>
        /// 具體數據庫名稱
        /// </summary>
        public string DbName { get; set; }
    }

創建一個分頁實體類

    /// <summary>
    /// 描述：分頁實體
    /// 創建人：蘇本東
    /// 創建時間：2019-3-5 19:05:20
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class PagingModel<T> where T : class, new()
    {
        /// <summary>
        /// 當前頁碼
        /// </summary>
        public int PageIndex { get; set; }

        /// <summary>
        /// 每頁大小
        /// </summary>
        public int PageSize { get; set; }

        /// <summary>
        /// 總記錄數
        /// </summary>
        public int TotalRecords { get; set; }

        /// <summary>
        /// 總頁數
        /// </summary>
        public int TotalPages { get; set; }

        /// <summary>
        /// 每頁數據
        /// </summary>
        public List<T> Items { get; set; }
    }

最后就是調用了

            FilterDefinition<ModbusData> filter = Builders<ModbusData>.Filter.Empty;
            if (request.Ip.IsNotNullAndEmpty())
            {
                //注意：Eq方法的第一個參數，大小寫需要跟數據庫一致，不然查詢無效
                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類是與MongoDB的表對應的

提供兩篇文章供學習參考：

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

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