Access a Control from any Class

You'll need to somehow maintain a reference to the form after you open it, so you can refer to the control. If you want to get to it from any class, then you'll need a public variable in one class (or in a module, in VB.NET) that refers to the form.

Also, you'll need to make sure that the Modifiers property on the control is set to Friend or Public, so it's "visible" outside the parent form. Then, you can refer to the public variable that refers to your form, and work with the control as a property of that form.

For example, if you have code like this:

Public frm As MyForm

then somewhere else, you add

frm = New MyForm()

and if you've set TextBox1 so that it's visible outside MyForm's class, then you should be able to use code like this from any other class:

MessageBox.Show(frm.TextBox1.Text)

Thank you very much.
I'm going to implement some Functions to
access the Controls. You really helped me a lot.

First of all, I must confess that I agree TOTALLY with Erymuzuan Mustapa's comment--I would never, ever expose a control as a public member of a form. But to keep this simple...

Anyway, nothing happens with the form because you never displayed the form. You need:

Dim frm As New Form1()

Sub Test()
frm.Textfield1.text = "Test"
frm.Show()
End sub

The fact that TextField1 showed up in the IntelliSense list of available properties should tell you that the concept is working. Also, if you're only using the variable frm in one place, it can be local to the procedure. I just assumed you wanted to be able to get at it from multiple locations.

just to throw a comment on top of all of this: UserControls are great for wrapping functionality, like sections of forms that will be used more than once on different forms, etc. Just like everything else, they're just a class, so you can write whatever methods you need to wrap functionality of your "form" to use when you have instances of your UserControls on all of your Forms.