C#_JDBC连接数据库

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using System.Data.SqlClient;
 using System.Data;

 namespace MySchool.DAL
 {
     public class DBHelper
     {
         //private const string conn = "Data Source=.;Initial Catalog=MySchool;User ID=GaoFei;Password=111111";
         private const string conn = "Data Source=.;Initial Catalog=MySchool;User ID=sa;Password=sa";
         private static SqlConnection connection = new SqlConnection(conn);

         /// <summary>
         /// 读取数据
         /// </summary>
         /// <returns></returns>
         public static SqlDataReader Reader(string sql)
         {
             try
             {
                 connection.Open();
                 SqlCommand comm = new SqlCommand(sql, connection);
                 return comm.ExecuteReader(CommandBehavior.CloseConnection);
             }
             catch (Exception ex)
             {
                 throw;
             }
         }

         /// <summary>
         /// 增删改数据
         /// </summary>
         /// <param name="sql"></param>
         /// <returns></returns>
         public static int ExecuteNonQuery(string sql)
         {
             try
             {
                 connection.Open();   //打开数据库连接
                 SqlCommand comm = new SqlCommand(sql, connection);
                 return comm.ExecuteNonQuery();
             }
             catch (Exception ex)
             {
                 throw;
             }
             finally
             {
                 connection.Close();
             }
         }
         /// <summary>
         /// 返回单个值
         /// </summary>
         /// <param name="sql"></param>
         /// <returns></returns>
         public static object ExecuteScalar(string sql)
         {
             try
             {
                 connection.Open();   //打开数据库连接
                 SqlCommand comm = new SqlCommand(sql, connection);
                 return comm.ExecuteScalar();

             }
             catch (Exception)
             {
                 throw;
             }
             finally
             {
                 connection.Close();
             }
         }
         /// <summary>
         /// 返回数据集
         /// </summary>
         /// <param name="sql"></param>
         /// <param name="tableName"></param>
         /// <returns></returns>
         public static DataSet Fill(string sql, string tableName)
         {
             try
             {
                 connection.Open();  //打开连接
                 //创建数据适配器对象
                 SqlDataAdapter sda = new SqlDataAdapter(sql, connection);
                 //创建数据集
                 DataSet ds = new DataSet();
                 sda.Fill(ds, tableName); //填充数据集
                 return ds;
             }
             catch (Exception ex)
             {
                 throw;
                 //将异常引发出现
                 //  throw new Exception(e.Message);
             }
             finally
             {
                 connection.Close();
             }
         }
     }
 }