1) Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.
When you concatenate strings, you cause problems because SQL receives commands like:
SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'
The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:
SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;
Which SQL sees as three separate commands:
SELECT * FROM MyTable WHERE StreetAddress = 'x';
A perfectly valid SELECT
DROP TABLE MyTable;
A perfectly valid "delete the table" command
And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.
So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?
2) When you execute a Click handler, no more changes will happen to the display until it exits: the UI thread is the only thing which executes the Paint event, and it's tied up running your Click handler code, then objects don't get Painted. So the first progress bar value setting won't do anything useful as it will never be seen.
3) You can move that code (or at least the fixed version) onto a separate thread, but then you can't access the controls such as the ProgressBar directly - trying to do so will cause a cross threading error as only the UI thread can have access to any control.
Try using a BackgroundWorker
] - it provides a reporting mechanism designed for progress reporting.