<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>