error connecting: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool

public void enqueue(object e)
{
      try
      {
            DataChangeEventArgs e113 = (DataChangeEventArgs)e;
            resetdatasource();
            for (i=0; i < e113.sts.Length; i++)
            {
                  int hour113 = e113.sts[i].TimeStampNet.Hour;
                  int minute113 = e113.sts[i].TimeStampNet.Minute;
                  int second113 = e113.sts[i].TimeStampNet.Second;
                  int millisecond113 = e113.sts[i].TimeStampNet.Millisecond;
                  int year113 = e113.sts[i].TimeStampNet.Year;
                  int month113 = e113.sts[i].TimeStampNet.Month;
                  int day113 = e113.sts[i].TimeStampNet.Day;
                  DateTime sdate113 = new DateTime(year113, month113, day113, hour113, minute113, second113, millisecond113);

                  DataRow row1 = dt.NewRow();
                  row1["itemID"] = e113.sts[i].HandleClient;
                  row1["paramvalue"] = convert.ToString(e113.sts[i].DataValue);
                  row1["date_logged1"] = sdate113.ToString("dd-MM-yyyy HH:mm:ss.fff");
                  row1["Quality"] = e113.sts[i].Quality;
                  row1["date_logged"] = DateTime.FromFileTime(e113.sts[i].TimeStamp);
                  dt.Rows.Add(row1);
            }
            var threadupdate = new Thread(update);//start new thread & instance
            threadupdate.Start(dt);
      }
      catch { }
}


public void update(object dtnew)
            {
                  try
                  {
                           MySqlConnection con = new MySqlConnection(LocalConnection.GetLocalConnetionStringmysql());
                              DataSet oldvalueds=new DataSet();
                              DataTable newupdateddata = new DataTable();
                              MySqlDataAdapter da;


                              MySqlTransaction trans;
                              if (con.State == ConnectionState.Closed)
                                    con.Open();//throws exception
                              trans = con.BeginTransaction();
                              da = new MySqlDataAdapter();
                              da.InsertCommand = new MySqlCommand("INSERT INTO parameter (itemID,paramvalue, date_logged1,Quality,date_logged) " +
                                                               "VALUES (@itemID, @paramvalue,@date_logged1,@Quality,@date_logged)" +
                                                               "ON DUPLICATE KEY UPDATE " +
                                                               "itemID=VALUES(itemID),paramvalue=VALUES(paramvalue),date_logged1=VALUES(date_logged1),Quality=VALUES(Quality),date_logged=VALUES(date_logged)", con);

                              da.InsertCommand.Parameters.Add("@itemID", MySqlDbType.VarChar, 250, "itemID");
                              da.InsertCommand.Parameters.Add("@paramvalue", MySqlDbType.VarChar, 250, "paramvalue");
                              da.InsertCommand.Parameters.Add("@date_logged1", MySqlDbType.VarChar, 250, "date_logged1");
                              da.InsertCommand.Parameters.Add("@Quality", MySqlDbType.VarChar, 250, "Quality");
                              da.InsertCommand.Parameters.Add("@date_logged", MySqlDbType.VarChar, 250, "date_logged");

              开发者_开发知识库             da.InsertCommand.Transaction = trans;
                              DataTable newupdateddt = (DataTable)dtnew;
                            int k = da.Update(newupdateddt);//exception thrown 2nd
                                 trans.Commit();
                                 con.Close();
                     }

                  catch(Exception ex) {

                     }
                  finally
                  {


                  }
            }
 

it will be thrown an exception like "error connecting: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached."

i will be set the timeout=200 in connection string this exception was thrown "Deadlock found when trying to get lock; try restarting transaction" thanks in advance

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You are setting up an open connection, etc - and not disposing it. It isn't actually clear to me why, since this is all for the adapter (da) that you don't actually seem to use. However: in general, you should use using around all such (IDisposable) objects:

using(var con = new MySqlConnection(...))
{
    ... all the code that uses the connection here ...
}

This ensures the object is disposed cleanly and quickly - putting the underlying connection back into the pool. The same applies to any other objects that implement IDisposable - for example, probably the transaction too.

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A reason of this error could be all the connections are in use and max pool size has been reached. Try increasing the Pool Size in the connection string for example Max Pool Size = 100.