UserControl with header and content - Allow dropping controls in content panel and Prevent dropping controls in header at design time

I wrote User Control (yay!). But I want it to behave as a container. But wait! I know about

[Designer("System.Windows.Forms.Design.ParentControlDesigner, System.Design", 
    typeof(IDesigner))]

Trick.

The problem is - I don't want all of my control to behave like container, but only one part. One - de facto - panel ;)

To give wider context: I wrote a control that has Grid, some common buttons, labels and functionalities. But it also has a part where the user is supposed to drop his custom buttons/controls whatever. Only in this particular part of the control, nowhere else.

Anyone had any idea?

You should do the following :

• For your user control, you need to create a new designer which enables the inner panel on design-time by calling EnableDesignMode method.
• For the inner panel, you need to create a designer which disables moving, resizing and removes some properties from designer.
• You should register the designers.

Example

You can read a blog post about this topic here and clone or download a working example:

• r-aghaei/ChildContainerControlDesignerSample
• Download Zip

Code

Here is the code for different elements of the solution.

Your user control

[Designer(typeof(MyUserControlDesigner))]
public partial class MyUserControl : UserControl
{
    public MyUserControl()
    {
        InitializeComponent();
        TypeDescriptor.AddAttributes(this.panel1,
            new DesignerAttribute(typeof(MyPanelDesigner)));
    }
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
    public Panel ContentsPanel
    {
        get { return panel1; }
    }
}

Designer for the inner panel

public class MyPanelDesigner : ParentControlDesigner
{
    public override SelectionRules SelectionRules
    {
        get
        {
            SelectionRules selectionRules = base.SelectionRules;
            selectionRules &= ~SelectionRules.AllSizeable;
            return selectionRules;
        }
    }
    protected override void PostFilterAttributes(IDictionary attributes)
    {
        base.PostFilterAttributes(attributes);
        attributes[typeof(DockingAttribute)] = 
            new DockingAttribute(DockingBehavior.Never);
    }
    protected override void PostFilterProperties(IDictionary properties)
    {
        base.PostFilterProperties(properties);
        var propertiesToRemove = new string[] {
            "Dock", "Anchor", "Size", "Location", "Width", "Height",
            "MinimumSize", "MaximumSize", "AutoSize", "AutoSizeMode",
            "Visible", "Enabled",
        };
        foreach (var item in propertiesToRemove)
        {
            if (properties.Contains(item))
                properties[item] = TypeDescriptor.CreateProperty(this.Component.GetType(),
                    (PropertyDescriptor)properties[item],
                    new BrowsableAttribute(false));
        }
    }
}

Designer for your user control

public class MyUserControlDesigner : ParentControlDesigner
{
    public override void Initialize(IComponent component)
    {
        base.Initialize(component);
        var contentsPanel = ((MyUserControl)this.Control).ContentsPanel;
        this.EnableDesignMode(contentsPanel, "ContentsPanel");
    }
    public override bool CanParent(Control control)
    {
        return false;
    }
    protected override void OnDragOver(DragEventArgs de)
    {
        de.Effect = DragDropEffects.None;
    }
    protected override IComponent[] CreateToolCore(ToolboxItem tool, int x,
        int y, int width, int height, bool hasLocation, bool hasSize)
    {
        return null;
    }
}