using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Reflection;
using Dapper;

namespace RecommendDAL.SqlHelper
{
    /// <summary>
    /// Dapper常用方法
    /// </summary>
    public class DapperHelper
    {
        private static readonly string connectionString = ConfigurationManager.ConnectionStrings["LJXDB"].ConnectionString;//LJXDB
        /// <summary>
        /// Dapper查询
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="param">参数</param>
        /// <returns></returns>
        public static DataTable SELECT(string sql, object param = null)
        {
            return ExecuteReader(sql, param);
        }
        private static DataTable ExecuteReader(string sql, object param = null)
        {
            string sqlStr = KeyValue.GetSqlStr(sql, param);//仅供调试用的SQL语句
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                try
                {
                    DataTable dt = new DataTable();
                    var reader = con.ExecuteReader(sql, param);
                    dt.Load(reader);
                    return dt;
                }
                catch
                {
                    return null;
                }
            }
        }
        /// <summary>
        /// 增加
        /// </summary>
        public static bool INSERT(string sql, object param = null)
        {
            return Execute(sql, param);
        }
        /// <summary>
        /// 修改
        /// </summary>
        public static bool UPDATE(string sql, object param = null)
        {
            return Execute(sql, param);
        }
        /// <summary>
        /// 删除
        /// </summary>
        public static bool DELETE(string sql, object param = null)
        {
            return Execute(sql, param);
        }
        /// <summary>
        /// Dapper增删改操作
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="param">参数</param>
        /// <returns></returns>
        private static bool Execute(string sql, object param = null)
        {
            string sqlStr = KeyValue.GetSqlStr(sql, param);//仅供调试用的SQL语句
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                try
                {
                    con.Execute(sql, param);
                    return true;
                }
                catch (Exception ex)
                {
                    var error = ex.Message;
                    return false;
                }
            }
        }
    }
    /// <summary>
    /// Dapper<泛型>,返回List<T>
    /// </summary>
    /// <typeparam name="T">泛型</typeparam>
    public class DapperHelper<T>
    {
        /// <summary>
        /// 数据库连接字符串
        /// </summary>
        private static readonly string connectionString = ConfigurationManager.ConnectionStrings["LJXDB"].ConnectionString;//LJXDB
        /// <summary>
        /// 查询列表
        /// </summary>
        /// <param name="sql">查询的sql</param>
        /// <param name="param">替换参数</param>
        /// <returns></returns>
        public static List<T> QueryToList(string sql, object param = null)
        {
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                try
                {
                    return con.Query<T>(sql, param).ToList();
                }
                catch
                {
                    return null;
                }
            }
        }
        public static List<T> SELECT(string sql, object param = null)
        {
            return QueryToList(sql, param);
        }
        /// <summary>
        /// 查询第一个数据
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns>返回序列中的第一个元素,如果源序列为空，则抛异常。</returns>
        public static T QueryFirst(string sql, object param = null)
        {
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                try
                {
                    return con.Query<T>(sql, param).ToList().First();
                }
                catch
                {
                    return default(T);
                }
            }
        }
        /// <summary>
        /// 查询第一个数据没有返回默认值
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns>返回序列中的第一个元素；如果序列中不包含任何元素，则返回默认值。</returns>
        public static T QueryFirstOrDefault(string sql, object param = null)
        {
            string sqlStr = KeyValue.GetSqlStr(sql, param);//仅供调试用的SQL语句
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                try
                {
                    return con.Query<T>(sql, param).ToList().FirstOrDefault();
                }
                catch
                {
                    return default(T);
                }
            }
        }
        /// <summary>
        /// 获取单条记录 返回实体<T>
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public static T TOP_1(string sql, object param = null)
        {
            return QueryFirstOrDefault(sql, param);
        }
        /// <summary>
        /// 查询单条数据
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns>返回序列的唯一元素；如果该序列并非恰好包含一个元素，则会引发异常。</returns>
        public static T QuerySingle(string sql, object param = null)
        {
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                try
                {
                    return con.Query<T>(sql, param).ToList().Single();
                }
                catch
                {
                    return default(T);
                }
            }
        }
        /// <summary>
        /// 查询单条数据,没有则返回默认值
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns>返回序列中满足指定条件的唯一元素；如果这类元素不存在，则返回默认值；如果有多个元素满足该条件，此方法将引发异常。</returns>
        public static T QuerySingleOrDefault(string sql, object param = null)
        {
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                try
                {
                    return con.Query<T>(sql, param).ToList().SingleOrDefault();
                }
                catch
                {
                    return default(T);
                }
            }
        }
        /// <summary>
        /// 增删改
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns>成功：true；失败：false；操作0行数据：true；</returns>
        public static bool Execute(string sql, object param = null)
        {
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                try
                {
                    con.Execute(sql, param);
                    return true;
                }
                catch (Exception ex)
                {
                    var error = ex.Message;
                    return false;
                }
            }
        }
        /// <summary>
        /// Reader获取数据
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public static IDataReader ExecuteReader(string sql, object param)
        {
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                try
                {
                    return con.ExecuteReader(sql, param);
                }
                catch
                {
                    return null;
                }
            }
        }
        /// <summary>
        /// Scalar获取数据
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public static object ExecuteScalar(string sql, object param)
        {
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                try
                {
                    return con.ExecuteScalar(sql, param);
                }
                catch
                {
                    return null;
                }
            }
        }
        /// <summary>
        /// Scalar获取数据
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public static T ExecuteScalarT(string sql, object param)
        {
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                try
                {
                    return con.ExecuteScalar<T>(sql, param);
                }
                catch
                {
                    return default(T);
                }
            }
        }
        /// <summary>
        /// 带参数的存储过程
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public static List<T> StoredProcedure(string proc, object param = null)
        {
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                try
                {
                    List<T> list = con.Query<T>(proc, param, null, true, null, CommandType.StoredProcedure).ToList();
                    return list;
                }
                catch
                {
                    return null;
                }
            }
        }
        /// <summary>
        /// 事务1 - 多条SQL语句数组
        /// </summary>
        /// <param name="sqlarr">多条SQL</param>
        /// <param name="param">param</param>
        /// <returns></returns>
        public static int ExecuteTransaction(string[] sqlarr)
        {
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                using (var transaction = con.BeginTransaction())
                {
                    try
                    {
                        int result = 0;
                        foreach (var sql in sqlarr)
                        {
                            result += con.Execute(sql, null, transaction);
                        }
                        transaction.Commit();
                        return result;
                    }
                    catch (Exception ex)
                    {
                        transaction.Rollback();
                        return 0;
                    }
                }
            }
        }
        /// <summary>
        /// 事务2 - 声明参数
        ///demo:
        ///dic.Add("Insert into Users values (@UserName, @Email, @Address)",
        ///        new { UserName = "jack", Email = "380234234@qq.com", Address = "上海" });
        /// </summary>
        /// <param name="Key">多条SQL</param>
        /// <param name="Value">param</param>
        /// <returns></returns>
        public static int ExecuteTransaction(Dictionary<string, object> dic)
        {
            using (SqlConnection con = new SqlConnection(connectionString))
            {
                using (var transaction = con.BeginTransaction())
                {
                    try
                    {
                        int result = 0;
                        foreach (var sql in dic)
                        {
                            result += con.Execute(sql.Key, sql.Value, transaction);
                        }
                        transaction.Commit();
                        return result;
                    }
                    catch (Exception ex)
                    {
                        transaction.Rollback();
                        return 0;
                    }
                }
            }
        }
    }
    /// <summary>
    /// 查看Dapper最终生成的SQL语句
    /// </summary>
    public class KeyValue
    {
        public string Key { get; set; }
        public string Value { get; set; }
        public static string GetSqlStr(string sql, object param = null)
        {
            try
            {
                string tempSql = sql;
                if (param != null)
                {
                    if (param.ToString().Contains("{") && param.ToString().Contains("}"))//匿名类型
                    {
                        string[] arr = param.ToString().Replace("{", "").Replace("}", "").Split(',');
                        List<KeyValue> paramList = new List<KeyValue>();
                        foreach (var item in arr)
                        {
                            KeyValue kv = new KeyValue();
                            string[] temp = item.Split('=');
                            kv.Key = temp[0].Trim();
                            kv.Value = temp[1].Trim();
                            paramList.Add(kv);
                        }
                        foreach (var par in paramList)
                        {
                            tempSql = tempSql.Replace("@" + par.Key, "'" + par.Value + "'");
                        }            
                    }
                    else//自定义实体类型
                    {               
                        Type type = param.GetType();
                        foreach (PropertyInfo p in type.GetProperties())
                        {                           
                            var Key = p.Name;      
                            var Value = p.GetValue(param);
                            tempSql = tempSql.Replace("@" + Key, "'" + Value + "'");
                        }
                    }
                }
                return tempSql;
            }
            catch
            {
                return sql;
            }
        }
    }
}

app.config / web.config ： 

<configuration>
  <connectionStrings>
    <add name="DB" connectionString="server=.;database=db;uid=sa;pwd=123456;integrated security=false;" />
  </connectionStrings>  
</configuration>

简单用法：

//查 无参数
var list = DapperHelper<T_User>.Query("select * from T_User ").ToList();
//查 带参数
var list = DapperHelper<T_User>.Query("select * from T_User where uid=@uid", new { uid = 1, }).ToList();
//增
int ins = DapperHelper<T_User>.Execute("insert into T_User (uid,username) value(@uid,@username)", new { uid = 1, username = "张三" });
//改
int upd = DapperHelper<T_User>.Execute("update T_User set username=@username where uid=@uid", new { username = "李四", uid = 1});
//删
int del = DapperHelper<T_User>.Execute("delete from T_User where uid=@uid", new { uid = 1 });

 查看Dapper最终生成的SQL语句的函数方法：https://blog.csdn.net/djk8888/article/details/108868166