Passing information to a form

We very often want to pass information into an Access form to change the behaviour of that form - perhaps it's the ID code of the client's order so that the form can display information about that order. Whatever the reason, there are three ways of doing this in Microsoft Access. One way is easy but wrong, one way is clever but clumsy, the third way is the best.

Global variables

The easiest way to get information into a form is to use a global variable. This will be available to all the program code in the database so you can store some information from one form and then retrieve it from another. It's very quick and easy but it does have it's dangers and it does make maintenance more difficult.

A global variable is convenient because it can be used from anywhere in the database but this convenience is also its greatest drawback. If you declare a global variable:

then you'll be able to let the user enter an order number before the form opens and still be able to read that order number when the form is running. That's solved your immediate problem but what will happen if another programmer wants to do the same thing in another part of the system some months later? If they choose to use the same technique and they accidentally use the same variable name then your original form might stop working. A global variable is just a bug that's waiting to happen.

Referring to an invisible textbox on another form

A clever programmer will know that it's possible to read the value of a textbox on another form. Something like:

will pick up the text from the textbox named 'txtOrderID' on the form named 'PickOrder'. The textbox doesn't need to be visible to the user so you can hide it behind something else or just set its Visible property false.

This is better than using a global variable but it does mean that these two forms are now tied together. The second form can only be called from the PickOrder form and if PickOrder isn't on screen then the second form will crash. It's a safe technique but it does restrict your flexibility.

Using the OpenArgs property

Every form has an OpenArgs property which holds the value of the parameter that was passed to the form. If you're wanting to pass "ABC123" in as the order id then just specify this as the value of the OpenArgs parameter when you open the form:

Pick the value up in the form's Load event:

and you've got a safe, easy way of getting a parameter into a form.

You can only pass a single parameter with OpenArgs but it is possible to pack multiple parameters into a single string argument.