简单易懂的三层架构全解析

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;
using System.Configuration;
using System.Data;

namespace 三层架构Demo.DAL
{
class SQLHelper
{
//public static readonly string connStr = System.Configuration.ConfigurationSettings.AppSettings["dbconnstr"];
//获得连接字符串
public static readonly string connStr =
ConfigurationManager.ConnectionStrings["dbconnstr"].ConnectionString;

/// <summary>
/// 执行方法ExecuteNonQuery
/// </summary>
/// <param name="cmdText">要执行的sql语句</param>
/// <param name="parameters">参数数组</param>
/// <returns>受影响的行数</returns>
public static int ExecuteNonQuery(string cmdText,
params SqlParameter[] parameters)
{
using (SqlConnection conn=new SqlConnection (connStr))
{
conn.Open();
using (SqlCommand cmd= conn.CreateCommand())
{
cmd.CommandText = cmdText;
cmd.Parameters.AddRange(parameters);
int i=cmd.ExecuteNonQuery();
return i;
}
}
}

/// <summary>
/// 执行ExecuteScalar() 返回第一行第一列数据
/// </summary>
/// <param name="cmdText">要执行的sql语句</param>
/// <param name="parameters">参数数组</param>
/// <returns>返回第一行第一列数据</returns>
public static object ExecuteScalar(string cmdText,
params SqlParameter[] parameters)
{
using (SqlConnection conn=new SqlConnection(connStr))
{
conn.Open();
using (SqlCommand cmd=conn.CreateCommand())
{
cmd.CommandText = cmdText;
cmd.Parameters.AddRange(parameters);
return cmd.ExecuteScalar();
}
}
}

/// <summary>
/// 执行ExecuteDataTable（）方法
/// </summary>
/// <param name="cmdText">要执行的Sql语句</param>
/// <param name="parameters">参数数组</param>
/// <returns>返回一个DataTable</returns>
public static DataTable ExecuteDataTable(string cmdText,
params SqlParameter[] parameters)
{
using (SqlConnection conn=new SqlConnection (connStr))
{
conn.Open();
using (SqlCommand cmd=conn.CreateCommand())
{
cmd.CommandText = cmdText;
cmd.Parameters.AddRange(parameters);
using ( SqlDataAdapter adapter=new SqlDataAdapter (cmd))
{
DataTable dt = new DataTable();
adapter.Fill(dt);
return dt;
}
}
}
}

/// <summary>
/// 执行ExecuteSqlDataReader()方法
/// </summary>
/// <param name="cmdText">要执行的Sql语句</param>
/// <param name="parameters">参数数组</param>
/// <returns>返回一个SqlDataReader</returns>

public static SqlDataReader ExecuteSqlDataReader(string cmdText,
params SqlParameter[] parameters)
{
using (SqlConnection conn=new SqlConnection (connStr))
{
conn.Open();
using (SqlCommand cmd=conn.CreateCommand())
{
cmd.CommandText = cmdText;
cmd.Parameters.AddRange(parameters);
return cmd.ExecuteReader();
}
}
}
}
}