Entity Framework with MySQL 学习笔记一(拦截)

参考 : http://msdn.microsoft.com/en-us/data/dn469464.aspx

EF 允许我们在发送SQL请求和返回数据时做一些拦截的动作

比如可以自定义写 log ，修改command , 修改result 等等

这里只是给一个简单的例子，以后有用到才研究吧.

    public class EFInterceptorForSetTimeZone : IDbCommandInterceptor 
    {       
        public void NonQueryExecuting(DbCommand command, DbCommandInterceptionContext<int> interceptionContext)
        {
           
        }
        public void NonQueryExecuted( DbCommand command, DbCommandInterceptionContext<int> interceptionContext)
        {
            
        }
        public void ReaderExecuting( DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)
        {
            command.CommandText = "set time_zone = '-8:00';" + command.CommandText; 
        }
        public void ReaderExecuted(DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)
        {
            //use table to load result then modify then convert back to reader
            var dataTable = new DataTable();
            dataTable.Load(interceptionContext.Result);
            dataTable.Rows[0]["id"] = 55555;
            interceptionContext.Result = dataTable.CreateDataReader();
        }

        public void ScalarExecuting( DbCommand command, DbCommandInterceptionContext<object> interceptionContext)
        {
           
        }
        public void ScalarExecuted(DbCommand command, DbCommandInterceptionContext<object> interceptionContext)
        {
          
        }
        private void LogIfNonAsync<TResult>(DbCommand command, DbCommandInterceptionContext<TResult> interceptionContext)
        {
            
        }
        private void LogIfError<TResult>(DbCommand command, DbCommandInterceptionContext<TResult> interceptionContext)
        {
           
        } 
    }
    protected void Page_Load(object sender, EventArgs e)
    {
        try
        {
            using (DB db = new DB())
            {
                DbInterception.Add(new EFInterceptorForSetTimeZone()); //添加一个拦截器

                //拦截for写log, 放一个委托函数就可以了，
                //msg 就是entity pass 进来的 string 
                //function (msg) { do something with no return.. };
                db.Database.Log = msg =>
                {
                    string y = msg;
                };
                var xyz = db.admins.ToList();
            }
        }
        catch (Exception ex)
        {
            string x = ex.Message; 
        }
    }