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 ?? ;
                 }
             }
             catch (Exception ex)
             {
                 Logs.Write(LogType.Error, ex.Message, this.GetType());
                 return -;
             }
         }
         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 -;
             }
         }
         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 -;
             }
         }
         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 ;
             }
             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！