i want know what kind of problems cause this error. i am using C# with firebird databse after some use my project i have seen this error "TIMEOUT EXCEEDED" i have closed and rechecked all connection() and all reader(). but same problem can someone plz take me out this problem ? sory plz i cant post my huge code

In my experience you either have a very long query running (whic you would most likely know about) or the app has stalled waited for connections to be released (which you mention you have checked). You can increase the connection pool to see if that fixes the problem - if it doesn then you know the number of open connections is the issue.