sqlhelper.cs

比较好的异步数据库访问示例

		/// <returns>asynchronous result object</returns>
		public static IAsyncResult BeginExecuteNonQuery
			(IDbConnection connection, CommandType commandType, string commandText, AsyncCallback ac, Object state, params IDataParameter[] commandParameters)
		{
			ExecuteNonQueryDelegate5 d = new ExecuteNonQueryDelegate5(ExecuteNonQuery);
			IAsyncResult result = d.BeginInvoke(connection, commandType, commandText, commandParameters, ac, state);
			return result;
		}

		/// <summary>
		/// Execute a stored procedure via a command (that returns no resultset) against the specified IDbConnection 
		/// using the provided parameter values.  This method will query the database to discover the parameters for the 
		/// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
		/// </summary>
		/// <param name="connection">a valid IDbConnection</param>
		/// <param name="spName">the name of the stored procedure</param>
		/// <param name="ac">callback object containing a delegate</param>
		/// <param name="state">state object supplied by the client</param>
		/// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
		/// <returns>asynchronous result object</returns>
		public static IAsyncResult BeginExecuteNonQuery
			(IDbConnection connection, string spName, AsyncCallback ac, Object state, params object[] parameterValues)
		{
			ExecuteNonQueryDelegate6 d = new ExecuteNonQueryDelegate6(ExecuteNonQuery);
			IAsyncResult result = d.BeginInvoke(connection, spName, parameterValues, ac, state);
			return result;
		}

		/// <summary>
		/// Execute a command that returns no resultset
		/// </summary>
		/// <param name="transaction">a valid IDbTransaction</param>
		/// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">the stored procedure name or T-SQL command</param>
		/// <param name="ac">callback object containing a delegate</param>
		/// <param name="state">state object supplied by the client</param>
		/// <returns>asynchronous result object</returns>
		public static IAsyncResult BeginExecuteNonQuery
			(IDbTransaction transaction, CommandType commandType, string commandText, AsyncCallback ac, Object state)
		{
			ExecuteNonQueryDelegate7 d = new ExecuteNonQueryDelegate7(ExecuteNonQuery);
			IAsyncResult result = d.BeginInvoke(transaction, commandType, commandText, ac, state);
			return result;
		}

		/// <summary>
		/// Execute a command that returns no resultset
		/// </summary>
		/// <param name="transaction">a valid IDbTransaction</param>
		/// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">the stored procedure name or T-SQL command</param>
		/// <param name="ac">callback object containing a delegate</param>
		/// <param name="state">state object supplied by the client</param>
		/// <param name="commandParameters">an array of IDataParameters used to execute the command</param>
		/// <returns>asynchronous result object</returns>
		public static IAsyncResult BeginExecuteNonQuery
			(IDbTransaction transaction, CommandType commandType, string commandText, AsyncCallback ac, Object state, params IDataParameter[] commandParameters)
		{
			ExecuteNonQueryDelegate8 d = new ExecuteNonQueryDelegate8(ExecuteNonQuery);
			IAsyncResult result = d.BeginInvoke(transaction, commandType, commandText, commandParameters, ac, state);
			return result;
		}

		/// <summary>
		/// Execute a stored procedure via a SqlCommand (that returns no resultset) against the specified 
		/// IDbTransaction using the provided parameter values.  This method will query the database to discover the parameters for the 
		/// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
		/// </summary>
		/// <param name="transaction">a valid IDbTransaction</param>
		/// <param name="spName">the name of the stored procedure</param>
		/// <param name="ac">callback object containing a delegate</param>
		/// <param name="state">state object supplied by the client</param>
		/// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
		/// <returns>asynchronous result object</returns>
		public static IAsyncResult BeginExecuteNonQuery
			(IDbTransaction transaction, string spName, AsyncCallback ac, Object state, params object[] parameterValues)
		{
			ExecuteNonQueryDelegate9 d = new ExecuteNonQueryDelegate9(ExecuteNonQuery);
			IAsyncResult result = d.BeginInvoke(transaction, spName, parameterValues, ac, state);
			return result;
		}

		/// <summary>
		/// Receive the result at the end of an asynchronous call.
		/// </summary>
		/// <param name="result">asynchronous result object</param>
		/// <returns>an int representing the number of rows affected by the command</returns>
		public static int EndExecuteNonQuery(IAsyncResult result)
		{
			if ((((AsyncResult)result).AsyncDelegate).GetType() == typeof(ExecuteNonQueryDelegate1))
			{
				ExecuteNonQueryDelegate1 d = (ExecuteNonQueryDelegate1) ((AsyncResult)result).AsyncDelegate;
				return d.EndInvoke(result);
			}
			else if ((((AsyncResult)result).AsyncDelegate).GetType() == typeof(ExecuteNonQueryDelegate2))
			{
				ExecuteNonQueryDelegate2 d = (ExecuteNonQueryDelegate2) ((AsyncResult)result).AsyncDelegate;
				return d.EndInvoke(result);
			}
			else if ((((AsyncResult)result).AsyncDelegate).GetType() == typeof(ExecuteNonQueryDelegate3))
			{
				ExecuteNonQueryDelegate3 d = (ExecuteNonQueryDelegate3) ((AsyncResult)result).AsyncDelegate;
				return d.EndInvoke(result);
			}
			else if ((((AsyncResult)result).AsyncDelegate).GetType() == typeof(ExecuteNonQueryDelegate4))
			{
				ExecuteNonQueryDelegate4 d = (ExecuteNonQueryDelegate4) ((AsyncResult)result).AsyncDelegate;
				return d.EndInvoke(result);
			}
			else if ((((AsyncResult)result).AsyncDelegate).GetType() == typeof(ExecuteNonQueryDelegate5))
			{
				ExecuteNonQueryDelegate5 d = (ExecuteNonQueryDelegate5) ((AsyncResult)result).AsyncDelegate;
				return d.EndInvoke(result);
			}
			else if ((((AsyncResult)result).AsyncDelegate).GetType() == typeof(ExecuteNonQueryDelegate6))
			{
				ExecuteNonQueryDelegate6 d = (ExecuteNonQueryDelegate6) ((AsyncResult)result).AsyncDelegate;
				return d.EndInvoke(result);
			}
			else if ((((AsyncResult)result).AsyncDelegate).GetType() == typeof(ExecuteNonQueryDelegate7))
			{
				ExecuteNonQueryDelegate7 d = (ExecuteNonQueryDelegate7) ((AsyncResult)result).AsyncDelegate;
				return d.EndInvoke(result);
			}
			else if ((((AsyncResult)result).AsyncDelegate).GetType() == typeof(ExecuteNonQueryDelegate8))
			{
				ExecuteNonQueryDelegate8 d = (ExecuteNonQueryDelegate8) ((AsyncResult)result).AsyncDelegate;
				return d.EndInvoke(result);
			}
			else //if ((((AsyncResult)result).AsyncDelegate).GetType() == typeof(ExecuteNonQueryDelegate9))
			{
				ExecuteNonQueryDelegate9 d = (ExecuteNonQueryDelegate9) ((AsyncResult)result).AsyncDelegate;
				return d.EndInvoke(result);
			}
		}


		#endregion ExecuteNonQuery

		#region ExecuteScalar
		
		/// <summary>
		/// Execute a command (that returns a 1x1 resultset) using the provided parameters.
		/// </summary>
		/// <param name="connection">a valid IDbConnection</param>
		/// <param name="transaction">a valid IDbTransaction</param>
		/// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">the stored procedure name or T-SQL command</param>
		/// <param name="commandParameters">an array of IDataParameters used to execute the command</param>
		/// <returns>an object containing the value in the 1x1 resultset generated by the command</returns>
		private static object ExecuteScalar(IDbConnection connection, IDbTransaction transaction, CommandType commandType, string commandText, params IDataParameter[] commandParameters)
		{
			//create a command and prepare it for execution
			SqlCommand cmd = new SqlCommand();
			ConnectionState connState = connection.State;
			PrepareCommand(cmd, connection, transaction, commandType, commandText, commandParameters);
			
			//execute the command & return the results
			object retval;
			try
			{
				retval = cmd.ExecuteScalar();
			}
			catch (SqlException e)
			{
				//Handle data access exception condition
				LogException(e);
				//Wrap the current exception and re-throw the new exception
				throw e;
			}
			finally
			{
				// detach the IDataParameters from the command object, so they can be used again.
				cmd.Parameters.Clear();
				if (connState == ConnectionState.Closed)
				{
					connection.Close();
				}
			}
			return retval;
		}
		/// <summary>
		/// Execute a command (that returns a 1x1 resultset) using the provided parameters.
		/// </summary>
		/// <param name="connectionString">a valid connection string for a IDbConnection yet to be opened</param>
		/// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">the stored procedure name or T-SQL command</param>
		/// <returns>an object containing the value in the 1x1 resultset generated by the command</returns>
		public static object ExecuteScalar(string connectionString, CommandType commandType, string commandText)
		{
			//pass through the call providing null for the set of IDataParameters
			return ExecuteScalar(connectionString, commandType, commandText, (SqlParameter[])null);
		}

		/// <summary>
		/// Execute a command (that returns a 1x1 resultset) using the provided parameters.
		/// </summary>
		/// <param name="connectionString">a valid connection string for a IDbConnection yet to be opened</param>
		/// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">the stored procedure name or T-SQL command</param>
		/// <param name="commandParameters">an array of IDataParameters used to execute the command</param>
		/// <returns>an object containing the value in the 1x1 resultset generated by the command</returns>
		public static object ExecuteScalar(string connectionString, CommandType commandType, string commandText, params IDataParameter[] commandParameters)
		{
			//create & open a IDbConnection, and dispose of it after we are done.
			using (SqlConnection cn = new SqlConnection(connectionString))
			{
				//call the overload that takes a connection in place of the connection string
				return ExecuteScalar(cn, commandType, commandText, commandParameters);
			}
		}

		/// <summary>
		/// Execute a stored procedure via a command (that returns a 1x1 resultset) against the database specified in 
		/// the connection string using the provided parameter values.  This method will query the database to discover the parameters for the 
		/// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
		/// </summary>
		/// <param name="connectionString">a valid connection string for a IDbConnection</param>
		/// <param name="spName">the name of the stored procedure</param>
		/// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
		/// <returns>an object containing the value in the 1x1 resultset generated by the command</returns>
		public static object ExecuteScalar(string connectionString, string spName, params object[] parameterValues)
		{
			//if we receive parameter values, we need to figure out where they go
			if ((parameterValues != null) && (parameterValues.Length > 0)) 
			{
				//pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
				SqlParameter[] commandParameters = (SqlParameter[])SqlHelperParameterCache.GetSpParameterSet(connectionString, spName);

				//assign the provided values to these parameters based on parameter order
				AssignParameterValues(commandParameters, parameterValues);

				//call the overload that takes an array of IDataParameters
				return ExecuteScalar(connectionString, CommandType.StoredProcedure, spName, commandParameters);
			}
				//otherwise we can just call the SP without params
			else 
			{
				return ExecuteScalar(connectionString, CommandType.StoredProcedure, spName);
			}
		}

		/// <summary>
		/// Execute a command (that returns a 1x1 resultset) using the provided parameters.
		/// </summary>
		/// <param name="connection">a valid IDbConnection</param>