DataSet

强类型DataSet

  private void button3_Click(object sender, EventArgs e)<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

        {

           

  //表名+TableAdapter，表名+DataTable，表名+Row，然后用解析来填充类名

           　　T_PersonsTableAdapter  adapter=new T_PersonsTableAdapter();

               DataSet封装与使用.DataSet1.T_PersonsDataTable data= adapter.GetData();

              for(int i=0;i<data.Count;i++)

              {

                  //遍历读取每行的字段

 

                  DataSet封装与使用.DataSet1.T_PersonsRow personsRow = data[i];

                  MessageBox.Show(personsRow.UserName + personsRow.Password);

 

 

              }

 =========

dataset用法

DataSet用法:<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

        private void button1_Click(object sender, EventArgs e)

        {

             string connStr = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;

             using (SqlConnection conn = new SqlConnection(connStr))

             {

                 conn.Open();

                 using (SqlCommand cmd = conn.CreateCommand())

                 {

                     cmd.CommandText = "select * from T_persons";

                     DataSet dataset = new DataSet();  //放查询出的数据

                     SqlDataAdapter adapter = new SqlDataAdapter(cmd); //存放打算执行的语句

                     adapter.Fill(dataset); //fill内部执行，把结果放在dataset中

                     DataTable table = dataset.Tables[0]; //执行结果

                     for (int i = 0; i < table.Rows.Count; i++)  //遍历datatable的每一行

                     {

                         DataRow row = table.Rows[i]; //得到每一行

                         string name = Convert.ToString(row["Name"]); //得到每一列的值

                         MessageBox.Show(name);

                     }

 

                 }

             }

        }

============

Datase封装

 

class SQLHelper

{

  public  static  DataTable ExecuteDataTable(string sql, params  SqlParameter[] parameters)

   { 

    String connStr = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;

   using(SqlConnection conn = new  SqlConnection(connStr))

    {

           conn.Open();

           using(SqlCommand  cmd  =conn.CreateCommand())

          {

             cmd.Command.Text=sql; //清除旧数据

             foreach(SqlParameter  parameter  in  parameters)

              {

                  cmd.parameters.Add(parameter); 

               }

             DataSet dataset= new DataSet();

             SqlDataAdapter adapter = new SqlDataAdapter(cmd);

            adapter.Fill(dataset);

            return dataset.Tables[0];

         }

      }

   }

}

---------------------------

private void button1_Click(object sender, EventArgs e)

        {

            DataTable dt = SQLHelper.ExecuteDataTable("select * from T_persons");

            for (int i = 0; i < dt.Rows.Count; i++)

            {

                DataRow row = dt.Rows[i];

                string name = Convert.ToString(row["name"]); //row[]返回object类型

            }

        }

}

==========================

简单登录2

  private void btnLogin_Click(object sender, EventArgs e)<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

        {

            DataTable dt = SQLHelper.ExecuteDataTable("select * from T_Persons where UserName=@username", new SqlParameter("username", txtName.Text));

 

            if (dt.Rows.Count >= 1)

            {

              //判断ErrorTimes次数

                DataRow row = dt.Rows[0];

                int  errortimes = Convert.ToInt32(row["ErrorTimes"]);

                if (errortimes >= 3)

                {

                    MessageBox.Show("错误次数过多!");

                    return;

                }

               string password =Convert.ToString(row["Password"]);

               if (password == txtPwd.Text)

               {

                   MessageBox.Show("登录成功!");

                   //错误次数清零

SQLHelper.ExecuteNonQuery("update T_Persons set ErrorTimes=0 where UserName=@username", new SqlParameter("username", txtName.Text));

               }

               else

               {

              

                  //错误次数加1

                   SQLHelper.ExecuteNonQuery("update T_Persons set ErrorTimes=ErrorTimes+1 where UserName=@username", new SqlParameter("username", txtName.Text));

                     MessageBox.Show("密码错误!");

               }

            }

            else

            {

                MessageBox.Show("用户名错误!!!");

            }

        }

===============

C#入门尝试封装

classSQLHelper<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

    {

        publicstaticint ExecuteNonQuery(string sql, paramsSqlParameter[] parameters)    //表示sqlcommand参数类型

        {

            string connStr = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;

        using(SqlConnection conn = newSqlConnection(connStr))  //创建连接并打开

        {

            conn.Open();

            using (SqlCommand cmd = conn.CreateCommand())

            {

                cmd.CommandText = sql;

                foreach (SqlParameter parameter in parameters)

                {

                    cmd.Parameters.Add(parameter);  //遍历参数

 

                }

                return cmd.ExecuteNonQuery();  //执行非查询

            }

        }

        }

    }

-----------------

C#入门尝试封装

classSQLHelper<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

    {

        publicstaticint ExecuteNonQuery(string sql, paramsSqlParameter[] parameters)    //表示sqlcommand参数类型

        {

            string connStr = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;

        using(SqlConnection conn = newSqlConnection(connStr))  //创建连接并打开

        {

            conn.Open();

            using (SqlCommand cmd = conn.CreateCommand())

            {

                cmd.CommandText = sql;

                foreach (SqlParameter parameter in parameters)

                {

                    cmd.Parameters.Add(parameter);  //遍历参数

 

                }

                return cmd.ExecuteNonQuery();  //执行非查询

            }

        }

        }

    }