<appSettings>
  <add key="webpages:Version" value="2.0.0.0" />
  <add key="webpages:Enabled" value="false" />
  <add key="PreserveLoginUrl" value="true" />
  <add key="ClientValidationEnabled" value="true" />
  <add key="UnobtrusiveJavaScriptEnabled" value="true" />
  <add key="con" value="server=.\sqlexpress; user id = sa;password = a123456;database = xsgl1;max pool size=512;"/>
 </appSettings>
 <connectionStrings>
  <add name="conSql" connectionString="server=(local)\sqlexpress; User Id = sa;password = a123456;database = xsgl1;max pool size=512;"/>
 </connectionStrings> 

Configuration

 public class HomeController : Controller
  {
   //
   // GET: /Home/
 
   public ActionResult Index()
   {
    #region connect sql function one
    SqlConnectionStringBuilder one = new SqlConnectionStringBuilder();
    one.DataSource = "(local)\\sqlexpress";
   one.InitialCatalog = "xsgl1";
    one.UserID = "sa";
    one.Password = "a123456";
    one.MaxPoolSize = 512;
    SqlConnection sct = new SqlConnection(one.ConnectionString);
    #endregion
    #region connect sql function two
    //string conn = ConfigurationManager.AppSettings["con"].ToString();
    //SqlConnection sct = new SqlConnection(conn);
    #endregion
    #region connect sql function three
    //string conn = ConfigurationManager.ConnectionStrings["conSql"].ConnectionString;
    //SqlConnection sct = new SqlConnection(conn);
    #endregion
    SqlCommand scm = new SqlCommand();
    scm.Connection = sct;
   scm.CommandType = CommandType.Text;
    scm.CommandText = "select 课程名 from kc where 课程号='A001'";
    sct.Open();
    SqlDataReader sdr = scm.ExecuteReader();
    if (sdr.Read())
    {
    ViewBag.hao = sdr["课程名"];
   }
   sdr.Close();
   return View();
  }
  public ActionResult About()
  {
   return View();
   }
  }

Controller

@{
 ViewBag.Title = "Index";
 }
 @ViewBag.hao
 <h2>Index</h2>