Question

I’m getting something pretty strange going on when trying to read some data using the MySql .net connector. Here’s the code:

IDataReader reader = null;  using (MySqlConnection connection = new MySqlConnection(this.ConnectionString)) {     String getSearch = 'select * from organization';     MySqlCommand cmd = new MySqlCommand(getSearch, connection);     cmd.CommandType = CommandType.Text;      connection.Open();     reader = cmd.ExecuteReader();      while (reader.Read())     {         // response write some stuff to the screen (snipped for brevity)     } } 

If I put a breakpoint after the ExecuteReader and expand the results view in Visual Studio (hovering over reader and expanding), I can see the rows returned by the query. If I then let that close and expand the results view again, I get the message ‘Enumeration yielded no results’.

It seems as if the contents of the reader are getting reset as soon as they’re viewed.

As for what we’ve tried:
– the SQL runs fine directly on to DB
– Binding the results of the query directly to a datagrid just returns an empty datagrid
– got the latest version of the .net connector
– tried on two different machines to rule out any local errors

So far nothing’s worked.

If anyone could offer any ideas or suggestions they would be very much appreciated.

Answer 1

from what I understand the SqlDataReader is intended to be used for a one-time enumeration of the data you’ve returned. Once you’ve cycled through the results once, the object has done its duty. Here are a couple ideas for working around this, one or the other of which may solve this for you depending on your needs:

1. Re-execute the query to generate another SqlDataReader when needed

2. Instead of using the SqlDataReader, store the results of your original query into a System.Data.DataTable, where you can then re-read and manipulate the data however you like.

Hope this helps!

Adam