Question

I am making a user control in MS Visual C#, and there is one thing that I just can’t find an answer to:

How do I limit which dimensions a control can be resized in during design view?

For a clear example of what I’m asking, the built in TrackBar control can only only be made wider, not taller, and only displays the resizing squares on the left and right in design mode. Is there a way to replicate this for a user control?

I have tried setting MinimumSize and MaximumSize values in the designer for my control, but this doesn’t give ideal results.

Answer 1

To get the full behavior you’re talking about (no adorners on top/bottom or left/right) and custom functionality inside the design time environment, you’ll probably have to resort to building a custom control designer for your control.

This is a huge topic, as there are a lot of things you can do. Effectively what you’d do is create a class that inherits from ControlDesigner, override whatever functionality you need, then register it on your user control with the DesignerAttribute, specifying typeof(IDesigner) for the 2nd parameter (and your custom ControlDesigner-derived type for the first).

Enhancing Design-time Support
Custom Designers
ControlDesigner class example
Custom Design-time Control Features in Visual Studio .NET

Now, in the case of TrackBar, it has its own designer that overrides the ControlDesigner.SelectionRules property. This property simply lets you return an enumeration value (it’s a Flags enum, so you can OR them together) indicating how your design-time selection adorners appear (or not appear). Once you’ve restricted design-time resizing via a designer, it’s simply up to your control itself to constrain its own size vai SetBoundsCore.