Hi,
use the Dock property and set it to Fill to always resize a control to the size of its container.
You could then use a SplitContainer as the outermost container in your form where it fills the complete form (Dock == Fill) and place two other controls in its left and right panel also with Dock == Fill. If you need more controls you could also put splitcontainer in splitcontainers. That depends on how you layout your controls and how many of them should be autosized.
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SvenC