Error “There is already an open DataReader associated with this Command which must be closed first” when using 2 distinct commands

Question

I have this legacy code :

 private void conecta()
 {  
     if (conexao.State == ConnectionState.Closed)
         conexao.Open();
 }

 public List

        

Answer 1

1. The optimal solution could be to try to transform your solution into a form where you don't need to have two readers open at a time. Ideally it could be a single query. I don't have time to do that now.

2. If your problem is so special that you really need to have more readers open simultaneously, and your requirements allow not older than SQL Server 2005 DB backend, then the magic word is MARS (Multiple Active Result Sets). http://msdn.microsoft.com/en-us/library/ms345109%28v=SQL.90%29.aspx. Bob Vale's linked topic's solution shows how to enable it: specify MultipleActiveResultSets=true in your connection string. I just tell this as an interesting possibility, but you should rather transform your solution.

   • in order to avoid the mentioned SQL injection possibility, set the parameters to the SQLCommand itself instead of embedding them into the query string. The query string should only contain the references to the parameters what you pass into the SqlCommand.