After docking, this has to be the coolest layout feature. Anchoring is a little simpler than docking, but it can be a powerful tool. Using a graphical property editor (see Figure 3.8), you can set the Anchor property for a control to any combination of Top, Left, Bottom, and/or Right.
Figure 3.8
The property editor for anchoring is a nice little graphical control.
To anchor a control to a specific side means that the distance between the control and that side of its container becomes fixed. Therefore, if you anchor a control to a specific side and then resize the form, the control's distance from the anchored side(s) will not change. To maintain a constant position relative to one or more sides of your container, the control might have to be resized when the form's size changes.
By default, controls are anchored to the top and left, which makes them behave exactly as controls did in previous versions of Visual Basic. When you resize the form, they do not move or resize. If you want to create a TextBox that grows as you make your form wider, you can anchor it to the top, left, and right sides. If you want the TextBox to grow in height as well as width, anchor it to the bottom as well. Figure 3.9 shows a form with some anchored controls, and Figure 3.10 shows what happens when that form is resized. You will see a few more examples of how anchoring can be used to lay out your form in the samples throughout the rest of this book.
Figure 3.9
Anchored controls maintain a fixed distance between themselves and the container edge(s) they are anchored to.
Figure 3.10
As the form changes size, the controls move and resize automatically.
AutoScrolling Forms
Docking and anchoring are designed to resize your controls when the form is resized, but resizing the contents of your form is not always appropriate. In some cases there is a minimum size at which your form is usable, so resizing below that needs to be avoided. There are also situations when the content on your form is a fixed size, making resizing inappropriate. Windows forms provides a few additional features to allow you to deal with these situations. Forms have minimum/maximum height and width properties (allowing you to constrain resizing to a specific range of sizes) and the AutoScroll feature. AutoScroll allows a form to be resized by the users, but instead of shrinking the controls on the form, scroll bars appear to allow the users to view the entire form area even if they have resized the window. The form shown in Figure 3.11 is a perfect candidate for AutoScroll ; it contains a large number of controls and buttons and cannot be resized using docking or anchoring.
Figure 3.11
This form would be hard to resize, so the solution is to allow users to scroll.
If the user were to resize this form, making it smaller than the area required for all of its controls, the AutoScroll feature of Windows forms will save the day by adding horizontal and/or vertical scroll bars as required (see Figure 3.12 ).
Figure 3.12
AutoScroll automatically adds scroll bars when the form becomes small enough to hide any part of any of the controls on the form.
In addition to the AutoScroll property, which you set to True to enable auto scrolling, there are two other properties, AutoScrollMargin and AutoScrollMinSize , that are used to configure exactly how scrolling occurs.
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