初学者问题：数据库放在类里的写法？

Question

public class DataAccess
{
     public SqlConnection OpenConn()
     {
        string  myConnectionString = System.Configuration.ConfigurationSettings.AppSettings["BaseDbConnectionString"].ToString();

SqlConnection MyConnection = new SqlConnection (myConnectionString);
MyConnection.Open();
return MyConnection;
      }
}

Answer 1

同意 jiezhi(風依舊)
调用的时候，SqlConnection cn=new DataAccess().OpenConn();

Answer 2

public class DataCn
{
private SqlConnection MyConnection;
string myConnectionString="";
public  DataCn()
{
myConnectionString=System.Configuration.ConfigurationSettings.AppSettings["BaseDbConnectionString"].ToString();}
public DataCn(string ConnectionString)
{
   myConnectionString=ConnectionString;   
}
public void GetCn(bool IsOpen)
{
MyConnection = new SqlConnection (myConnectionString);
if(IsOpen)
{
MyConnection.Open();
}
return MyConnection;
}
public void Close()
{
  MyConnection.Close();
}
}

Answer 3

using System;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;namespace BidData
{
/// <summary>
/// Class1 的摘要说明。
/// </summary>
public class Conn
{
String strConn = "";
SqlConnection _conn;
public Conn()
{
//
// TODO: 在此处添加构造函数逻辑
//
strConn = ConfigurationSettings.AppSettings["connBid"];
}
public SqlConnection GetConn()
{
if (_conn == null)
{
_conn = new SqlConnection(strConn);
}
if (_conn.State != ConnectionState.Open)
{
try
{
_conn.Open();
}
catch
{
throw new Exception("数据库连接错误");
}
}
return _conn;
}
}
}