I would like to know what is the best practice to check that data on an entry form is correct and what are the advantages and disadvantages of each?

I have seen this type of checking in one of 3 places:

1) At the point where the data is captured (for example in the valid event of say a text box.

2) A number of check are done in a method on the form. This method is called before the tableupdate is issued.

3) Checks are written into a stored procedure. This procedure is then called each time before the referential integrity is run for a trigger in the table.


Thanks in advance!