dapper之连接数据库（Oracle，SQL Server，MySql）

　　因为项目需求，需要项目同时可以访问三个数据库，因此本人经过一番研究，得出以下代码。

　　

1.建立公共连接抽象类(DataBase)

public abstract class DataBase
    {
        /// <summary>
        /// 
        /// </summary>
        public abstract string ConnectionString { get; }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="cmd"></param>
        /// <param name="pName"></param>
        /// <param name="value"></param>
        /// <param name="type"></param>
        /// <returns></returns>

        public DbParameter CreateParameter(DbCommand cmd, String pName, Object value, System.Data.DbType type)
        {
            var p = cmd.CreateParameter();
            p.ParameterName = pName;
            p.Value = (value == null ? DBNull.Value : value);
            p.DbType = type;
            return p;
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public abstract DbConnection CreateConnection(); 
        /// <summary>
        /// 返回List
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sql"></param>
        /// <param name="paramObject"></param>
        /// <returns></returns>
        public List<T> Select<T>(string sql, Object paramObject = null)
        {
             
            try
            {
                using (DbConnection conn = CreateConnection())
                {
                    conn.Open();
                    var list = Dapper.SqlMapper.Query<T>(conn, sql, paramObject);
                    return list.ToList<T>();
                }
             
            }
            catch (Exception ex)
            {
                Logs.Write(LogType.Error, ex.Message,this.GetType());
                return null;
            }
        }
        /// <summary>
        /// 返回List
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="tabName">表名</param>
        /// <param name="paramObject"></param>
        /// <returns></returns>
        public List<T> Select<T>()
        { 
            try
            {
                using (DbConnection conn = CreateConnection())
                {
                    conn.Open();
                    var list = Dapper.SqlMapper.Query<T>(conn, "SELECT * FROM " + typeof(T).Name, null);
                    return list.ToList<T>();
                }
            }
            catch (Exception ex)
            {
                Logs.Write(LogType.Error, ex.Message, this.GetType());
                return null;
            }
        }
        public int Insert<T>(T t)
        {
            try
            {
                using (DbConnection conn = CreateConnection())
                {
                    conn.Open();
                    var id = conn.Insert(t);
                    return id ?? 0;
                }
            }
            catch (Exception ex)
            {
                Logs.Write(LogType.Error, ex.Message, this.GetType());
                return -1;
            }
        }
        public int Delete<T>(T t)
        {
            try
            {
                using (DbConnection conn = CreateConnection())
                {
                    conn.Open();
                    return conn.Delete(t); 
                }
            }
            catch (Exception ex)
            {
                Logs.Write(LogType.Error, ex.Message, this.GetType());
                return -1;
            }
        }
        public int Update<T>(T t)
        {
            try
            {
                using (DbConnection conn = CreateConnection())
                {
                    conn.Open();
                    return conn.Update(t); 
                }
            }
            catch (Exception ex)
            {
                Logs.Write(LogType.Error, ex.Message, this.GetType());
                return -1;
            }
        }
        public string InsertByGuid<T>(T t)
        {
            try
            {
                using (DbConnection conn = CreateConnection())
                {
                    conn.Open();
                    return conn.Insert<string,T>(t); 
                }
            }
            catch (Exception ex)
            {
                Logs.Write(LogType.Error, ex.Message, this.GetType());
                return "";
            }
        }
        public List<T> GetList<T>(string sql, Object paramObject = null)
        {
            try
            {
                using (DbConnection conn = CreateConnection())
                {
                    conn.Open();
                    return conn.Query<T>(sql, paramObject).ToList();
                }
            }
            catch (Exception ex)
            {
                Logs.Write(LogType.Error, ex.Message, this.GetType());
                return null;
            }
        }
        public IEnumerable<dynamic> GetList(string sql, Object paramObject = null)
        {
            try
            {
                using (DbConnection conn = CreateConnection())
                {
                    conn.Open();
                    return conn.Query(sql, paramObject);
                }
            }
            catch (Exception ex)
            {
                Logs.Write(LogType.Error, ex.Message, this.GetType());
                return null;
            }
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="paramObject"></param>
        /// <returns></returns>
        public List<dynamic> Select(string sql, Object paramObject = null)
        {
            DbConnection conn = null;
            try
            {
                conn = CreateConnection();
                conn.Open();
                var list = Dapper.SqlMapper.Query(conn, sql, paramObject);
                return list.ToList<dynamic>();
            }
            catch (Exception ex)
            {
                Logs.Write(LogType.Error, ex.Message, this.GetType());
                return null;
            }
            finally
            {
                if (conn != null)
                    conn.Close();
            }
        }

        /// <summary>
        /// 获取一条数据
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="paramObject"></param>
        /// <returns></returns>
        public dynamic Single(string sql, Object paramObject = null)
        {
            DbConnection conn = null;
            try
            {
                conn = CreateConnection();
                conn.Open();
                var list = Dapper.SqlMapper.QuerySingleOrDefault<dynamic>(conn, sql, paramObject);
                return list;
            }
            catch (Exception ex)
            {
                Logs.Write(LogType.Error, ex.Message, this.GetType());
                return null;
            }
            finally
            {
                if (conn != null)
                    conn.Close();
            }
        }

        /// <summary>
        /// 获取一条数据
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sql"></param>
        /// <param name="paramObject"></param>
        /// <returns></returns>
        public T Single<T>(string sql, Object paramObject = null)
        {

            DbConnection conn = null;
            try
            {
                conn = CreateConnection();
                conn.Open();
                var list = Dapper.SqlMapper.QuerySingleOrDefault<T>(conn, sql, paramObject);
                return list;
            }
            catch (Exception ex)
            {
                Logs.Write(LogType.Error, ex.Message, this.GetType());
                return default(T);
            }
            finally
            {
                if (conn != null)
                    conn.Close();
            }
        }

        /// <summary>
        /// 获取一行一列
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sql"></param>
        /// <param name="paramObject"></param>
        /// <returns></returns>
        public T ExecuteScalar<T>(string sql, Object paramObject = null)
        {

            DbConnection conn = null;
            try
            {
                conn = CreateConnection();
                conn.Open();
                T t = Dapper.SqlMapper.ExecuteScalar<T>(conn, sql, paramObject);
                return t;
            }
            catch (Exception ex)
            {
                Logs.Write(LogType.Error, ex.Message, this.GetType());
                return default(T);
            }
            finally
            {
                if (conn != null)
                    conn.Close();
            }
        }

        /// <summary>
        /// 返回受影响行数
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="paramObject"></param>
        /// <returns></returns>
        public int Execute(string sql, Object paramObject = null)
        {
            DbConnection conn = null;
            try
            {
                conn = CreateConnection();
                conn.Open();
                int count = Dapper.SqlMapper.Execute(conn, sql, paramObject);
                return count;
            }
            catch (Exception ex)
            {
                Logs.Write(LogType.Error, ex.Message, this.GetType());
                return 0;
            }
            finally
            {
                if (conn != null)
                    conn.Close();
            }
        }
    }

2.建立3个不同数据库连接类（OracleDataBase、SqlDataBase、MySqlDataBase）继承(DataBase)类

public class OracleDataBase : DataBase
    {
        public override string ConnectionString
        {
            get
            {
                return System.Configuration.ConfigurationManager.ConnectionStrings["OracleConnection"].ToString();
            }
        }
        /// <summary>
        /// 常用
        /// </summary>
        /// <returns></returns>
        public override DbConnection CreateConnection()
        {
            Oracle.ManagedDataAccess.Client.OracleConnection conn = new Oracle.ManagedDataAccess.Client.OracleConnection(ConnectionString);
            conn.ConnectionString = ConnectionString;
            return null;
        }
    }

public class SqlDataBase : DataBase
    {
        /// <summary>
        /// 
        /// </summary>
        public override string ConnectionString
        {
            get
            {
                return System.Configuration.ConfigurationManager.ConnectionStrings["SqlConnection"].ToString();
            }
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public override DbConnection CreateConnection()
        {
            SqlConnection conn = new SqlConnection(ConnectionString);
            conn.ConnectionString = ConnectionString;
            return conn;
        }
        
    }

public  class MySqlDataBase : DataBase
    {
        /// <summary>
        /// 
        /// </summary>
        public override string ConnectionString
        {
            get
            {
                return System.Configuration.ConfigurationManager.ConnectionStrings["MySqlConnection"].ToString();
            }
        }
        /// <summary>
        /// 常用
        /// </summary>
        /// <returns></returns>
        public override DbConnection CreateConnection()
        {
            MySql.Data.MySqlClient.MySqlConnection conn = new MySql.Data.MySqlClient.MySqlConnection(ConnectionString); 
            return conn;
        }
    }

3.访问不同的连接

 public List<T> GetList<T>()
        {
            var db = new SqlDataBase();
            return db.Select<T>();
        }
        public List<T> GetList<T>()
        {
            var db = new OracleDataBase();
            return db.Select<T>();
        }
        public List<T> GetList<T>()
        {
            var db = new MySqlDataBase();
            return db.Select<T>();
        }

以上代码就是访问不同的数据库的列表信息，其他增删改和上面的差不多写法，如果还有其他问题，请评论！