！！！SqlHelper 传智！

DataSet离线数据集  
 一般查询调用就用DataSet 将SQLserver数据库查询数据储存在vs操作内存中随时用随时遍历   以防做项目时突然与数据库断开连接，操作受限数据丢失带来的麻烦   若数据确实很大我们则用SqlDataReader dr=cmd.ExcuteReader()  

   using (SqlConnection conn = new SqlConnection(@"server=PC-20150619EMUEasb;Database=test;user=ewrw;pwd=463828"))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "select*from youdao where pwd=@pwd";
                    cmd.Parameters.Add(new SqlParameter("@pwd", txt.Text));
                    SqlDataAdapter adapter = new SqlDataAdapter(cmd);
                    DataSet dataset = new DataSet();
                    adapter.Fill(dataset);
                    DataTable table = dataset.Tables[0];
                    DataRowCollection rows = table.Rows;
                    for (int i = 0; i < rows.Count; i++)
                    {
                        DataRow row = rows[i];
                        int Age = (int)row["age"];
                        string name = (string)row["name"];

                    }
                }



            }

SqlHelper类建立绑定数据库增删改查

步骤：

一，右键项目--新建项--添加App.config应用配置文件以便项目以后客户联接别的服务器数据库好更改

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <connectionStrings>
    <add name="dbConnstr"  connectionString="server=.;Database=test;user=sa;pwd=32"/>
  </connectionStrings>
</configuration>

二，右键引用 --添加引用 System.Configuration 　　

三，

      /// <summary>
      /// 使用长度可变参数来简化    
      /// </summary>
      /// <param name="sql"></param>
      /// <param name="parameters"></param>
      /// <returns></returns>

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

namespace WpfApplication2
{
class SqlHelper
{//调用APP.config配置文件中客户需要连接的数据库字符串
private static string connStr = ConfigurationManager.ConnectionStrings["dbconnstr"].ConnectionString;

//封装数据的原则把不变的写到方法里，把变化的放到参数中

// 增删改的操作
public static int ExecuteNonQuery(string sql, params SqlParameter[] parameters)
{
using (SqlConnection conn = new SqlConnection(connStr))//建立数据库联接 using释放空间
{
conn.Open();
using (SqlCommand cmd = conn.CreateCommand())//创建操作数据库的命令
{
cmd.CommandText = sql;
cmd.Parameters.AddRange(parameters);
return cmd.ExecuteNonQuery();//执行操作的命令
}
}

}
// 查询返回一条结果的操作如Count(*) ,sum()等..
public static object ExecuteScalar(string sql, params SqlParameter[] parameters)
{
using (SqlConnection conn = new SqlConnection(connStr))
{
conn.Open();
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.CommandText = sql;
cmd.Parameters.AddRange(parameters); // foreach(SqlParameter param in parameters)
//{
// cmd.Parameters.Add(param);
// }

return cmd.ExecuteScalar();
}
}

}
// DataSet离线查询结果返回表结构操作：一般项目操作里面只有一个表所以直接返回一个表更方便
public static DataTable ExecuteDataTable(string sql, params SqlParameter[] parameters)
{
using (SqlConnection conn = new SqlConnection(connStr))
{
conn.Open();
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.CommandText = sql;
cmd.Parameters.AddRange(parameters);
SqlDataAdapter adapter = new SqlDataAdapter(cmd);
DataSet dataset = new DataSet();
adapter.Fill(dataset);
return dataset.Tables[0];
}
}

}
//DateSet 完整封装方式：
//public static DataSet ExecuteDataSet(string sql,params SqlParameter[] parameters)
//{using (SqlConnection conn=new SqlConnection(connStr))
// {
// conn.Open();
// using(SqlCommand cmd=conn.CreateCommand())
// {
// cmd.CommandText=sql;
// cmd.Parameters.AddRange(parameters);
// SqlDataAdapter adapter=new SqlDataAdapter(cmd);
// DataSet dataset=new DataSet();
// adapter.Fill(dataset);
// return dataset;
// }
// }
//}

////ExcuteReader 大数据联接数据库查询
//public static SqlDataReader ExcuteReader(string sql, params SqlParameter[] parameters)
//{
// using (SqlConnection conn = new SqlConnection(connStr))
// {
// conn.Open();
// using (SqlCommand cmd = conn.CreateCommand())
// {
// cmd.CommandText = sql;
// cmd.Parameters.AddRange(parameters);

// return cmd.ExecuteReader();
// }
// }

//}
}
}

主页面后台如何调用SqlHelper类？？

  private void Button_Click_2(object sender, RoutedEventArgs e)
        {
           SqlHelper.ExecuteNonQuery("insert into youdao(,,) values(@user,@pwd)",new SqlParameter[]{new SqlParameter("@user",500),new SqlParameter("@pwd","cdascas")});
            DataTable table=SqlHelper.ExecuteDataTable("select*from youdao where user=@user,pwd=@pwd", new SqlParameter[] { new SqlParameter("@user", 500), new SqlParameter("@pwd", "cdascas") });
/*..............................................................................................................................*/           


 //长度可变参数来简化后调用     不用传数组new SqlParameters[],只传对象即可
            DataTable table = SqlHelper.ExecuteDataTable("select*from youdao where user=@user,pwd=@pwd",new SqlParameter("@user", 500), new SqlParameter("@pwd", "cdascas") );
        foreach(DataRow row in table.Rows)
        {
            string user = (string)row["user"];
        }
      
  DataSet dataset = SqlHelper.ExecuteDataSet("select*from youdao where user=@user,pwd=@pwd", new SqlParameter[] { new SqlParameter("@user", 500), new SqlParameter("@pwd", "cdascas") });
        foreach (DataRow row in table.Tables[0].Rows)
       {
          string user = (string)row["user"];
       }
        }

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