Hallo,

aktuell bin ich so weit gekommen.

   MySqlCommand cmd = connection.CreateCommand();
			
   MySqlTransaction transaction = connection.BeginTransaction();

   cmd.Connection = connection;
   cmd.Transaction = transaction;

   try
	 {
        cmd.CommandText = "SELECT * FROM writeplc WHERE LEFT(plcvarname," + plcname.Length + ") = " + "'" +
				                  plcname + "'";
	    cmd.ExecuteNonQuery();

	    cmd.CommandText = "DELETE FROM writeplc WHERE LEFT(plcvarname," + plcname.Length + ") = " + "'" +
				                  plcname + "'";
        cmd.ExecuteNonQuery();

        if (Program.debuglevel == 2)
	     { Console.WriteLine("Write data read and deleted."); }
     }
			catch (Exception ex)
			{
				Console.WriteLine("Error reading write data for PLC {0}", ex.GetType());
				Console.WriteLine("Message: {0}", ex.Message);

				// Attempt to roll back the transaction.
				try 
				{ transaction.Rollback(); }
				catch (Exception ex2)
				{
					Console.WriteLine("Rollback Exception Type: {0}", ex2.GetType());
					Console.WriteLine("  Message: {0}", ex2.Message);
				}
			}

			// gelesene Schreibwerte auswerten
			MySqlDataReader rdr = cmd.ExecuteReader();

Beim 2. cmd.ExecuteNonQuery(); stützt das Programm ab. Wenn ich die "DELETE .... " in meinen mysql Script Editor eingeben, wird alles wie gewünsch gelöscht.

Bitte um Hiiiiiiiilfe 😉

Danke !!