Please Check you connection string which you are using to connect with you database.In connection string you must specify database user ID and password.

Check this article it is using grid view control and java script for keeping the state of check boxes. Maintaining States of Selected CheckBoxes in Different Pages

No it is not possible with this MessageBox.Show(). you need to design your own message box type form to accomplish this task.

Yes we can what you need to do is to add your assembly under the database programmability folder in assemblies and then call it in your query.

Yes we can do that but we need Mono framework for that. It will much better work if you compile your code with mono framework on linux then it will work correctly.