代码之家 › 专栏 › 技术社区 › Ruben Versavel

如果数据库中的值发生更改,如何持续更新该值

wpf database mysql c#

Ruben Versavel · 技术社区 · 8 年前

我试图在WPF应用程序中实现当前登录用户的状态。我可以从数据库中读取并设置该值一次,但我需要它来不断更新。例如,当一个用户在线时,他变为忙碌。该值将联机,但一旦在数据库上更改为“忙”,该值也将更新为“忙”。

例如:

  connection = new MySqlConnection(connectionString);
  Query = "SELECT status FROM Accounts WHERE username=@username";
  connection = new MySqlConnection(connectionString);

  MySqlCommand command = new MySqlCommand(Query, connection);
  command.CommandType = System.Data.CommandType.Text;
  command.Parameters.AddWithValue("@username", thedesiredusername);
  connection.Open();
  MySqlDataReader dataReader = command.ExecuteReader();

  while (dataReader.Read())
  {
     string userstatus = dataReader.GetString("status");
  }

这将设置userstatus值一次。我怎样才能让它做这样的事情:

connection = new MySqlConnection(connectionString);
Query = "SELECT status FROM Accounts WHERE username=@username";
connection = new MySqlConnection(connectionString);

MySqlCommand command = new MySqlCommand(Query, connection);
command.CommandType = System.Data.CommandType.Text;
command.Parameters.AddWithValue("@username", thedesiredusername);
connection.Open();
MySqlDataReader dataReader = command.ExecuteReader();

while (dataReader.Read())
{
   //keep doing:
   if (userstatus != dataReader.GetString("status"))
   {
     string userstatus = dataReader.GetString("status");
   }

}

提前感谢!