从c#处理到MySql的Connections的最佳方法是什么？

Question

我正在研究连接到MySql服务器的ac#应用程序.大约有20个函数将连接到数据库.该应用程序将部署在200台以上的机器上.我使用以下代码连接到我的数据库,这对所有功能都是相同的.问题是,我可以在200多台机器上部署时,某些连接没有关闭并且仍然存在.

连接字符串:

<add key="Con_Admin" value="server=test-dbserver; database=test_admindb; uid=admin; password=1Password; Use Procedure Bodies=false;" />

应用程序[Global.cs]中的全局声明连接字符串:

public static MySqlConnection myConn_Instructor = new MySqlConnection(ConfigurationSettings.AppSettings["Con_Admin"]);

查询数据库的功能:

  public static DataSet CheckLogin_Instructor(string UserName, string Password)
        {
            DataSet dsValue = new DataSet();
            //MySqlConnection myConn = new MySqlConnection(ConfigurationSettings.AppSettings["Con_Admin"]);
            try
            {
                string Query = "SELECT accounts.str_nric AS Nric, accounts.str_password AS `Password`," +
                        " FROM accounts " +
                        " WHERE accounts.str_nric = '" + UserName + "' AND accounts.str_password = '" + Password + "\'";

                MySqlCommand cmd = new MySqlCommand(Query, Global.myConn_Instructor);
                MySqlDataAdapter da = new MySqlDataAdapter();
                if (Global.myConn_Instructor.State == ConnectionState.Closed)
                {
                    Global.myConn_Instructor.Open();
                }

                cmd.ExecuteScalar();
                da.SelectCommand = cmd;
                da.Fill(dsValue);
                Global.myConn_Instructor.Close();
            }
            catch (Exception ex)
            {
                Global.myConn_Instructor.Close();
                ExceptionHandler.writeToLogFile(System.Environment.NewLine + "Target  :  " + ex.TargetSite.ToString() + System.Environment.NewLine + "Message :  " + ex.Message.ToString() + System.Environment.NewLine + "Stack   :  " + ex.StackTrace.ToString());
            }

            return dsValue;
        }

Answer 1

You should be using a unit-of-work approach using disposables. The MySqlConnection type is disposable, so should be cleanly wrapped in using blocks:

using (MySqlConnection connection = CreateConnection("Con_Admin")) {
  // Do work here.
}

What this does, is it ensures that Dispose() is called on the connection object, which closes the connection. This is incredibly important.

我也注意到你正在使用appSettings连接字符串,配置文件中实际上有一个专用的connectionStrings元素:

<connectionStrings>
  <add name="Con_Admin" connectionString="..." providerName="MySql.Data" />
</connectionStrings>

您可以使用它来创建连接实例:

public MySqlConnection CreateConnection(string name)
{
  if (string.IsNullOrEmpty(name))
    throw new ArgumentException("Connection name must be provided", "name");

  string connection = ConfigurationManager.ConnectionStrings[name].ConnectionString;
  return new MySqlConnection(connection);
}

最后一点,您应该尝试使用参数化查询,以防止SQL注入攻击:

string query = "SELECT * FROM SomeTable Where SomeField = @field";

using (MySqlCommand command = new MySqlCommand(query))
{
  command.Parameters.AddWithValue("@field", "someFieldValue");
}

希望有所帮助!