ConfigurationManager.ConnectionStrings 属性

public static ConnectionStringSettingsCollection ConnectionStrings { get; }

App.config

 <?xml version="1.0" encoding="utf-8" ?>
 <configuration>
     <startup>
         <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
     </startup>
     <connectionStrings>
       <add name="WingtipToys" connectionString="Data Source=(LocalDB)\v11.0;Initial Catalog=WingtipToys;Integrated Security=True;
Pooling=False" />
     </connectionStrings>
 </configuration>

如何使用连接字符串从数据库读取数据。

 using System;
 using System.Configuration;
 using System.Data.SqlClient;

 namespace ConsoleApplication1
 {
     class Program
     {
         static void Main(string[] args)
         {
             ReadProducts();
         }

         static void ReadProducts()
         {
             var connectionString = ConfigurationManager.ConnectionStrings["WingtipToys"].ConnectionString;
             string queryString = "SELECT Id, ProductName FROM dbo.Products;";
             using (var connection = new SqlConnection(connectionString))
             {
                 var command = new SqlCommand(queryString, connection);
                 connection.Open();
                 using (var reader = command.ExecuteReader())
                 {
                     while (reader.Read())
                     {
                         Console.WriteLine(String.Format("{0}, {1}", reader[], reader[]));
                     }
                 }
             }
         }
     }
 }