C#连接查询数据库

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

namespace 数据库学习
{
    class Program
    {
        static void Main(string[] args)
        {

//使用轻量级的SqlDataReader显示数据
            //指定Sql Server提供者的连接字符串
            string connString = "server=192.168.99.45;database =northwind;uid =sa;pwd=1";

            //建立连接对象

            SqlConnection Sqlconn = new SqlConnection(connString);
            //打开连接
            Sqlconn.Open();

            为上面的连接指定Command对象
            //SqlCommand thiscommand = Sqlconn.CreateCommand();
            //thiscommand.CommandText = "select customerID,companyName from customers";

            为指定的command对象执行DataReader
            //SqlDataReader thisSqlDataReader = thiscommand.ExecuteReader();

            只要有数据
            //while (thisSqlDataReader.Read())
            //{
            输出数据
            //    Console.WriteLine("\t{0}\t{1}", thisSqlDataReader["customerId"], thisSqlDataReader["companyName"]);
            //}
            关闭读取
            //thisSqlDataReader.Close();
            关闭连接
            //Sqlconn.Close();
            //Console.ReadLine();

//使用dataset显示数据

            // 查询字符串
            string   thisCommand = "select customerID,companyName from customers";

            //创建SqlDataAdapter对象,有两个参数，一个是查询字符串，一个是连接对象
            SqlDataAdapter SqlDap = new SqlDataAdapter(thisCommand,Sqlconn);
          
            //创建DataSet对象

            DataSet thisDataset = new DataSet();
           
            //使用SqlDataAdapter的Fill方法填充DataSet，有两个参数，一个是创建的DataSet实例，一个是填入的表

            SqlDap.Fill(thisDataset, "customers");

            //显示查询结果

            foreach (DataRow theRow in thisDataset.Tables["customers"].Rows)

            {
                Console.WriteLine(theRow["customerID"] + "\t" + theRow["companyName"]);
            }
            Sqlconn.Close();

            Console.ReadLine();

        }
    }
}