1 public class DbMasterSlaveCommandInterceptor : DbCommandInterceptor
 2     {
 3         private string masterConnectionString = "server=192.168.0.99;port=3306;user id=root;password=123456;persistsecurityinfo=True;database=testdb";
 4         private string slaveConnectionString = "server=192.168.0.101;port=3306;user id=root;password=123456;persistsecurityinfo=True;database=testdb";
 5         public override void ReaderExecuting(DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)
 6         {
 7             this.UpdateConnectionString(interceptionContext, this.slaveConnectionString);
 8         }
 9         public override void ScalarExecuting(DbCommand command, DbCommandInterceptionContext<object> interceptionContext)
10         {
11             this.UpdateConnectionString(interceptionContext, this.slaveConnectionString);
12         }
13         public override void NonQueryExecuting(DbCommand command, DbCommandInterceptionContext<int> interceptionContext)
14         {
15             this.UpdateConnectionString(interceptionContext, this.masterConnectionString);
16         }
17         private void UpdateConnectionString(DbInterceptionContext interceptionContext, string connectionString)
18         {
19             foreach (var context in interceptionContext.DbContexts)
20             {
21                 this.UpdateConnectionString(context.Database.Connection, connectionString);
22             }
23         }
24         private void UpdateConnectionString(DbConnection conn, string connectionString)
25         {
26             ConnectionState state = conn.State;
27             if (state == ConnectionState.Open)
28                 conn.Close();
29             conn.ConnectionString = connectionString;
30             if (state == ConnectionState.Open)
31                 conn.Open();
32         }
33     }

接着，在 Global.asax 的启动代码中将该 类型的实体注入 EF 全局执行上下文中。

1 public class MyHttpApplication : HttpApplication
2     {
3         protected void Application_Start()
4         {
5             DbInterception.Add(new DbMasterSlaveCommandInterceptor());
6         }
7     }

怎么样，原理是不是很简单？当然，如果想要实现一些丰富的配置和扩展功能，就还需要很多其他的代码了，关于这些本人将会在后续文章中逐步介绍！