C#数据库查询的基本步骤(Sql Server)

1. 连接字符串。一般定义在项目的web.config文件中。

   
     
                connectionString="data source=.\SQLEXPRESS; Initial Catalog=OnlineShoppingDatabase; Integrated Security=SSPI"
            providerName="System.Data.SqlClient" />
     

   public string connectionString = ConfigurationManager.ConnectionStrings["OnlineShopConnectionString"].ConnectionString;//通过ConfigurationManager获取连接字符串
2. 构建SqlConnection对象。

   SqlConnection connection = new SqlConnection(connectionString);

3. 打开连接。

   connection.Open();

4. 构建SqlCommand对象。根据不同的CommandType(Text,StoredProcedure,TableDirect)构建不同的SqlCommand对象。
   Text 即为sql语句。
   string sql="select * from Student";  SqlCommand command=new SqlCommand(sql,connection);
   StoredProcedure为存储过程。
   string storedProcdureName="procGetAllStudent";
   SqlCommand command=new SqlCommand(storedProcdureName,connection);
   command.CommandType=CommandType.StoredProcedure;//同时需指定CommandType
   //同时要为存储过程传参。遍历IDataParameter[].

   foreach (SqlParameter parameter in parameters)
                   {
                       command.Parameters.Add(parameter);
                   }

5. 根据需要的返回值类型，构建返回值。
   若期望得到SqlDataReader对象。SqlDataReader reader = command.ExecuteReader();
   若期望得到影响的行数。int row=command.ExecuteNonQuery();
   若期望得到DataSet/DataTable对象。
   DataTable dt = new DataTable();
   SqlDataAdapter adapter = new SqlDataAdapter();
   adapter.SelectCommand = command;
   adapter.Fill(dt);

6. 关闭连接。connection.Close();
   
   

以下是自己定义的数据库操作的相关类。

public sealed class ConnectionManager
    {
        private ConnectionManager() { }
        [ThreadStatic]
        public static SqlConnection sqlConnection;
        const string ConnectionString = "OnlineShopConnectionString";
        public static SqlConnection Connection
        {
            get
            {
                if (sqlConnection == null)
                {
                    sqlConnection = new SqlConnection(ConfigurationManager.ConnectionStrings[ConnectionString].ConnectionString);
                }
                return sqlConnection;
            }
        }
   }

 public sealed class SqlHelper
    {
        private SqlHelper()
        {
            //The class cannot be initialized.
        }
        

        /// 

        /// Gets a instance of sqlcommand
        /// 
         /// Represents an open sqlConnection to SQL Server database
        /// Stored procedure
        /// Parameter
        /// An object of sqlcommand
        private static SqlCommand BuildQueryCommand(SqlConnection sqlConnection, CommandType commandType, string commandText, IDataParameter[] parameters)
        {
            SqlCommand command = new SqlCommand(commandText, sqlConnection);
            command.CommandType = commandType;
            if (parameters != null)
            {
                foreach (SqlParameter parameter in parameters)
                {
                    command.Parameters.Add(parameter);
                }
            }
            return command;
        }
        public static SqlDataReader ExecuteReader(SqlConnection sqlConnection, CommandType commandType, string commandText, SqlParameter[] parameters)
        {
            if (null == sqlConnection)
            {
                throw new ArgumentNullException(Constant.ConnectionString);
            }
            SqlCommand command = BuildQueryCommand(sqlConnection, commandType, commandText, parameters);
            return command.ExecuteReader();
        }

        public static int ExecuteNonQuery(SqlConnection sqlConnection, CommandType commandType, string commandText, SqlParameter[] parameters)
        {
            if (null == sqlConnection)
            {
                throw new ArgumentNullException(Constant.ConnectionString);
            }
            SqlCommand command = BuildQueryCommand(sqlConnection, commandType, commandText, parameters);

            return command.ExecuteNonQuery();
        }
        
    }

C# 中数据库操作中的回归操作

private TransactionOptions options = new TransactionOptions();
            options.IsolationLevel = System.Transactions.IsolationLevel.ReadCommitted;
            options.Timeout = new TimeSpan(0, 0, 30); 

using (TransactionScope scope = new TransactionScope(TransactionScopeOption.Required, options))
            {
                try
                {

                    if (product.RetailPrice > product.DiscountPrice)
                    {
                        ConnectionManager.Connection.Open();
                        LogHelper.Log(string.Format(CultureInfo.CurrentCulture, Constant.AddProduct + product.ProductId));
                        result = DalProduct.AddProduct(ConnectionManager.Connection, product);
                    }
                    else
                    {
                        return false;
                    }
                    scope.Complete();
                }
                catch (Exception ex)
                {
                    LogHelper.Log(ex.Message);
                    throw;
                }
                finally
                {
                    if (ConnectionManager.Connection.State != ConnectionState.Closed)
                    {
                        ConnectionManager.Connection.Close();
                    }
                }
            }