学步园

      为什么我称之为最”原始“呢？在.NET刚诞生的时候，微软给出的示例项目PetShop第一版中用的就是SqlHelper——一个数据访问类（对象），实际上也就是一系列的方法，实现数据库的增、删、改、查等功能，包括使用T-SQL和存储过程。

　　PetShop相关下载：PetShop1、PetShop2、PetShop3、PetShop3.5、PetShop4、PetShop5

　　另外还有一个示例项目duwamish。 对比.NET PetShop和Duwamish来探讨Ado.NET的数据库编程模式。

       说到.NET数据访问，离不开ADO.NET ，关于ADO.NET的介绍，请参阅微软MSDN相关内容。使用ADO.NET可以访问多种数据库，如SQL Server、Oracle、Access等。

      Data Access Application Block for .NET代码及使用示例：代码中已经是使用示例，所以在此不举例子，你也可以直接下载下来看具体的示例。

      SqlHelper1.0代码：    
     

//===============================================================================
// Microsoft Data Access Application Block for .NET
// http://msdn.microsoft.com/library/en-us/dnbda/html/daab-rm.asp
//
// SQLHelper.cs
//
// This file contains the implementations of the SqlHelper and SqlHelperParameterCache
// classes.
//
// For more information see the Data Access Application Block Implementation Overview. 
// 
//===============================================================================
// Copyright (C) 2000-2001 Microsoft Corporation
// All rights reserved.
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY
// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT
// LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR
// FITNESS FOR A PARTICULAR PURPOSE.
//==============================================================================

using System;
using System.Data;
using System.Xml;
using System.Data.SqlClient;
using System.Collections;
namespace Microsoft.ApplicationBlocks.Data
{
    /// <summary>
    /// The SqlHelper class is intended to encapsulate high performance, scalable best practices for 
    /// common uses of SqlClient.
    /// </summary>
    public sealed class SqlHelper
    {
        #region private utility methods & constructors
        //Since this class provides only static methods, make the default constructor private to prevent 
        //instances from being created with "new SqlHelper()".
        private SqlHelper() {}
        /// <summary>
        /// This method is used to attach array of SqlParameters to a SqlCommand.
        /// 
        /// This method will assign a value of DbNull to any parameter with a direction of
        /// InputOutput and a value of null.  
        /// 
        /// This behavior will prevent default values from being used, but
        /// this will be the less common case than an intended pure output parameter (derived as InputOutput)
        /// where the user provided no input value.
        /// </summary>
        /// <param name="command">The command to which the parameters will be added</param>
        /// <param name="commandParameters">an array of SqlParameters tho be added to command</param>
        private static void AttachParameters(SqlCommand command, SqlParameter[] commandParameters)
        {
            foreach (SqlParameter p in commandParameters)
            {
                //check for derived output value with no value assigned
                if ((p.Direction == ParameterDirection.InputOutput) && (p.Value == null))
                {
                    p.Value = DBNull.Value;
                }
                
                command.Parameters.Add(p);
            }
        }
        /// <summary>
        /// This method assigns an array of values to an array of SqlParameters.
        /// </summary>
        /// <param name="commandParameters">array of SqlParameters to be assigned values</param>
        /// <param name="parameterValues">array of objects holding the values to be assigned</param>
        private static void AssignParameterValues(SqlParameter[] commandParameters, object[] parameterValues)
        {
            if ((commandParameters == null) || (parameterValues == null)) 
            {
                //do nothing if we get no data
                return;
            }
            // we must have the same number of values as we pave parameters to put them in
            if (commandParameters.Length != parameterValues.Length)
            {
                throw new ArgumentException("Parameter count does not match Parameter Value count.");
            }
            //iterate through the SqlParameters, assigning the values from the corresponding position in the 
            //value array
            for (int i = 0, j = commandParameters.Length; i < j; i++)
            {
                commandParameters[i].Value = parameterValues[i];
            }
        }
        /// <summary>
        /// This method opens (if necessary) and assigns a connection, transaction, command type and parameters 
        /// to the provided command.
        /// </summary>
        /// <param name="command">the SqlCommand to be prepared</param>
        /// <param name="connection">a valid SqlConnection, on which to execute this command</param>
        /// <param name="transaction">a valid SqlTransaction, or 'null'</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 SqlParameters to be associated with the command or 'null' if no parameters are required</param>
        private static void PrepareCommand(SqlCommand command, SqlConnection connection, SqlTransaction transaction, CommandType commandType, string commandText, SqlParameter[] commandParameters)
        {
            //if the provided connection is not open, we will open it
            if (connection.State != ConnectionState.Open)
            {
                connection.Open();
            }
            //associate the connection with the command
            command.Connection = connection;
            //set the command text (stored procedure name or SQL statement)
            command.CommandText = commandText;
            //if we were provided a transaction, assign it.
            if (transaction != null)
            {
                command.Transaction = transaction;
            }
            //set the command type
            command.CommandType = commandType;
            //attach the command parameters if they are provided
            if (commandParameters != null)
            {
                AttachParameters(command, commandParameters);
            }
            return;
        }
        #endregion private utility methods & constructors
        #region ExecuteNonQuery
        /// <summary>
        /// Execute a SqlCommand (that returns no resultset and takes no parameters) against the database specified in 
        /// the connection string. 
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders");
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</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 int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(string connectionString, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteNonQuery(connectionString, commandType, commandText, (SqlParameter[])null);
        }
        /// <summary>
        /// Execute a SqlCommand (that returns no resultset) against the database specified in the connection string 
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</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 SqlParamters used to execute the command</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(string connectionString, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create & open a SqlConnection, and dispose of it after we are done.
            using (SqlConnection cn = new SqlConnection(connectionString))
            {
                cn.Open();
                //call the overload that takes a connection in place of the connection string
                return ExecuteNonQuery(cn, commandType, commandText, commandParameters);
            }
        }
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns no 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>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        /// 
        /// e.g.:  
        ///  int result = ExecuteNonQuery(connString, "PublishOrders", 24, 36);
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="spName">the name of the stored prcedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(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 = 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 SqlParameters
                return ExecuteNonQuery(connectionString, CommandType.StoredProcedure, spName, commandParameters);
            }
                //otherwise we can just call the SP without params
            else 
            {
                return ExecuteNonQuery(connectionString, CommandType.StoredProcedure, spName);
            }
        }
        /// <summary>
        /// Execute a SqlCommand (that returns no resultset and takes no parameters) against the provided SqlConnection. 
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  int result = ExecuteNonQuery(conn, CommandType.StoredProcedure, "PublishOrders");
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</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 int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(SqlConnection connection, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteNonQuery(connection, commandType, commandText, (SqlParameter[])null);
        }
        /// <summary>
        /// Execute a SqlCommand (that returns no resultset) against the specified SqlConnection 
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  int result = ExecuteNonQuery(conn, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</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 SqlParamters used to execute the command</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {    
            //create a command and prepare it for execution
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, connection, (SqlTransaction)null, commandType, commandText, commandParameters);
            
            //finally, execute the command.
            int retval = cmd.ExecuteNonQuery();
            
            // detach the SqlParameters from the command object, so they can be used again.
            cmd.Parameters.Clear();
            return retval;
        }
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns no resultset) against the specified SqlConnection 
        /// 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>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        /// 
        /// e.g.:  
        ///  int result = ExecuteNonQuery(conn, "PublishOrders", 24, 36);
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</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 int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(SqlConnection connection, 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 = SqlHelperParameterCache.GetSpParameterSet(connection.ConnectionString, spName);
                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);
                //call the overload that takes an array of SqlParameters
                return ExecuteNonQuery(connection, CommandType.StoredProcedure, spName, commandParameters);
            }
                //otherwise we can just call the SP without params
            else 
            {
                return ExecuteNonQuery(connection, CommandType.StoredProcedure, spName);
            }
        }
        /// <summary>
        /// Execute a SqlCommand (that returns no resultset and takes no parameters) against the provided SqlTransaction. 
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  int result = ExecuteNonQuery(trans, CommandType.StoredProcedure, "PublishOrders");
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</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 int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(SqlTransaction transaction, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteNonQuery(transaction, commandType, commandText, (SqlParameter[])null);
        }
        /// <summary>
        /// Execute a SqlCommand (that returns no resultset) against the specified SqlTransaction
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  int result = ExecuteNonQuery(trans, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</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 SqlParamters used to execute the command</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(SqlTransaction transaction, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create a command and prepare it for execution
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, transaction.Connection, transaction, commandType, commandText, commandParameters);
            
            //finally, execute the command.
            int retval = cmd.ExecuteNonQuery();
            
            // detach the SqlParameters from the command object, so they can be used again.
            cmd.Parameters.Clear();
            return retval;
        }
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns no resultset) against the specified 
        /// SqlTransaction 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>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        /// 
        /// e.g.:  
        ///  int result = ExecuteNonQuery(conn, trans, "PublishOrders", 24, 36);
        ///











														

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