c# { 怎么把这段改成是连接sqlserver的而不是mysql？

protected void Button1_Click(object sender, EventArgs e)
{
string userName = Request.Form["userName"];
string password = Request.Form["password"];
int userState = 0;
try
{
userState = int.Parse(state.SelectedValue);
}
catch (ArgumentNullException ae)
{
}
}

//用Data类的DataConn方法确定作登录操作的用户是否是本系统已存在用户
int flag = new DataLogin().CheckUser(userName, password, userState);
//定义存入session的用户
AbstractUser user = null;
switch (flag)
{
case 1: user = new Teacher(userName, password, userState);
Session["user"] = user;
Response.Redirect("TeaHomePage.aspx");
break;
case 2: user = new Student(userName, password, userState);
Session.Add("user", user);
Response.Redirect("StuHomePage.aspx");
break;
case 3: user = new Manager(userName, password, userState);
Session.Add("user", user);
Response.Redirect("ManHomePage.aspx");
break;
case 0: error.Text = "用户名或者密码输入错误，请重新输入";
break;
case -1: Console.Write("数据库连接错误");
break;
}
}