.Net Core中Dapper的使用詳解

Dapper 是一個輕量級ORM框架，在項目中如果對性能比較看中，Dapper是一個不錯的選擇。接下來我們就來看看如何在項目中使用Dapper.

1.安裝Dapper

　　這里直接使用Nuget安裝。

 

 安裝完成之后，發現Nuget下已經有了Dapper。

2.創建DapperHelper

　　接下來創建一個DapperHelper幫助類，來進行讀取數據庫連接字符串，打開數據庫等操作。

代碼：

 public class DapperHelper
    {
        /// 數據庫連接名
        private static string _connection = string.Empty;

        /// 獲取連接名        
        private static string Connection
        {
            get { return _connection; }
            //set { _connection = value; }
        }

        /// 返回連接實例        
        private static IDbConnection dbConnection = null;

        /// 靜態變量保存類的實例        
        private static DapperHelper uniqueInstance;

        /// 定義一個標識確保線程同步        
        private static readonly object locker = new object();
        /// <summary>
        /// 私有構造方法，使外界不能創建該類的實例，以便實現單例模式
        /// </summary>
        private DapperHelper()
        {
            // 這里為了方便演示直接寫的字符串，實例項目中可以將連接字符串放在配置文件中，再進行讀取。
            _connection = @"server=.;uid=sa;pwd=sasasa;database=Dapper";
        }

        /// <summary>
        /// 獲取實例，這里為單例模式，保證只存在一個實例
        /// </summary>
        /// <returns></returns>
        public static DapperHelper GetInstance()
        {
            // 雙重鎖定實現單例模式，在外層加個判空條件主要是為了減少加鎖、釋放鎖的不必要的損耗
            if (uniqueInstance == null)
            {
                lock (locker)
                {
                    if (uniqueInstance == null)
                    {
                        uniqueInstance = new DapperHelper();
                    }
                }
            }
            return uniqueInstance;
        }


        /// <summary>
        /// 創建數據庫連接對象並打開鏈接
        /// </summary>
        /// <returns></returns>
        public static IDbConnection OpenCurrentDbConnection()
        {
            if (dbConnection == null)
            {
                dbConnection = new SqlConnection(Connection);
            }
            //判斷連接狀態
            if (dbConnection.State == ConnectionState.Closed)
            {
                dbConnection.Open();
            }
            return dbConnection;
        }
    }

 

　3.創建上下文 DbContext 作用是調用Dapper中操作數據庫的方法，里面是我自己封的一些常用方法，當然了這一步可以略去，直接調用也行，這里只是提供一種思路。

 

 public static class DbContext
    {
        // 獲取開啟數據庫的連接
        private static IDbConnection Db
        {
            get
            {
                //創建單一實例
                DapperHelper.GetInstance();
                return DapperHelper.OpenCurrentDbConnection();
            }
        }

        /// <summary>
        /// 查出一條記錄的實體
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static T QueryFirstOrDefault<T>(string sql, object param = null)
        {
            return Db.QueryFirstOrDefault<T>(sql, param);
        }

        public static Task<T> QueryFirstOrDefaultAsync<T>(string sql, object param = null)
        {
            return Db.QueryFirstOrDefaultAsync<T>(sql, param);
        }
        /// <summary>
        /// 查出多條記錄的實體泛型集合
        /// </summary>
        /// <typeparam name="T">泛型T</typeparam>
        /// <returns></returns>
        public static IEnumerable<T> Query<T>(string sql, object param = null, IDbTransaction transaction = null, bool buffered = true, int? commandTimeout = null, CommandType? commandType = null)
        {
            return Db.Query<T>(sql, param, transaction, buffered, commandTimeout, commandType);
        }

        public static Task<IEnumerable<T>> QueryAsync<T>(string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null)
        {
            return Db.QueryAsync<T>(sql, param, transaction, commandTimeout, commandType);
        }

        public static int Execute(string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null)
        {
            return Db.Execute(sql, param, transaction, commandTimeout, commandType);
        }

        public static Task<int> ExecuteAsync(string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null)
        {
            return Db.ExecuteAsync(sql, param, transaction, commandTimeout, commandType);
        }

        public static T ExecuteScalar<T>(string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null)
        {
            return Db.ExecuteScalar<T>(sql, param, transaction, commandTimeout, commandType);
        }

        public static Task<T> ExecuteScalarAsync<T>(string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null)
        {
            return Db.ExecuteScalarAsync<T>(sql, param, transaction, commandTimeout, commandType);
        }

        /// <summary>
        /// 同時查詢多張表數據（高級查詢）
        /// "select *from K_City;select *from K_Area";
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static SqlMapper.GridReader QueryMultiple(string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null)
        {
            return Db.QueryMultiple(sql, param, transaction, commandTimeout, commandType);
        }
        public static Task<SqlMapper.GridReader> QueryMultipleAsync(string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null)
        {
            return Db.QueryMultipleAsync(sql, param, transaction, commandTimeout, commandType);
        }
    }

 

接下來就可以調用了，DbContext.Action()