c# - Enumerate .Net control's items generically (MenuStrip, ToolStrip, StatusStrip)

Question

I've got some code that will generically get all Controls in a form and put them in a list. Here's some of the code:

        private List<Control> GetControlList(Form parentForm)
        {
            List<Control> controlList = new List<Control>();
            AddControlsToList(parentForm.Controls, controlList);

            return controlList;
        }

        private void AddControlsToList(Control.ControlCollection rootControls, List<Control> controlList)
        {
            foreach (Control c in rootControls)
            {
                controlList.Add(c);
                if (c.HasChildren)
                    AddControlsToList(c.Controls, controlList);
                //
            }
        }

So I'm only able to use c.HasChildren to check and see if there's any more child controls from this root control.

What about a menuStrip, toolStrip, and statusStrip? How do I get all of the controls that are in these controls generically? Ex: MenuStripItem

I know that I could try testing the c.GetType() == typeof(MenuStrip) but I was hoping to not have to do specific type tests.

If I need to give more info, please ask.

Thanks a bunch

Answer 1

I believe the VS designer does it by getting an instance of the control's designer (see the Designer attribute), and, if the designer is a ComponentDesigner, getting the AssociatedComponents property.

EDIT:

Okay, I guess that's a little vague. A warning, though: what follows is a little complicated, and might not be worth the effort.

A note on nomenclature:
Below, I will be referring to both the designer within Visual Studio—which is the name used to refer to the functionality within Visual Studio by which the layout and content of forms and controls are edited visually—and to designer classes—which will be explained below. To prevent confusion as to which I am referring to at any given time, I will always refer to the designer functionality within Visual Studio as "the designer", and I will always refer to a designer class as an "IDesigner", which is the interface each must implement.

When the Visual Studio designer loads a component (usually a control, but also things like Timer and such), it looks for a custom attribute on the class of type DesignerAttribute. (Those unfamiliar with attributes might want read up on them before continuing.)

This attribute, if present, provides the name of a class—an IDesigner—the designer can use to interface with the component. In effect, this class controls certain aspects of the designer and of the design-time behavior of the component. There's indeed quite a lot you can do with an IDesigner, but right now we're only interested in one thing.

Most controls that use a custom IDesigner use one that derives from ControlDesigner, which itself derives from ComponentDesigner. The ComponentDesigner class has a public virtual property called AssociatedComponents, which is meant to be overridden in derived classes to return a collection of references to all "child" components of this one.

To be more specific, the ToolStrip control (and by inheritance, the MenuStrip control) has a DesignerAttribute that references a class called ToolStripDesigner. It looks sort of like:

/*
 * note that in C#, I can refer to the "DesignerAttribute" class within the [ brackets ]
 * by simply "Designer".  The compiler adds the "Attribute" to the end for us (assuming
 * there's no attribute class named simply "Designer").
 */
[Designer("System.Windows.Forms.Design.ToolStripDesigner, System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"), ...(other attributes)]
public class ToolStrip : ScrollableControl, IArrangedElement, ...(other interfaces){
    ...
}

The ToolStripDesigner class is not public. It's internal to System.Design.dll. But since it's specified here by it's fully qualified name, the VS designer can use Activator.CreateInstance to create an instance of it anyway.

This ToolStripDesigner class, because it inherits [indirectly] from ComponentDesigner has an AssociatedComponents property. When you call it you get a new ArrayList that contains references to all the items that have been added to the ToolStrip.

So what would your code have to look like to do the same thing? Rather convoluted, but I think I have a working example:

/*
 * Some controls will require that we set their "Site" property before
 * we associate a IDesigner with them.  This "site" is used by the
 * IDesigner to get services from the designer.  Because we're not
 * implementing a real designer, we'll create a dummy site that
 * provides bare minimum services and which relies on the framework
 * for as much of its functionality as possible.
 */
class DummySite : ISite, IDisposable{
    DesignSurface designSurface;
    IComponent    component;
    string        name;

    public IComponent Component {get{return component;}}
    public IContainer Container {get{return designSurface.ComponentContainer;}}
    public bool       DesignMode{get{return false;}}
    public string     Name      {get{return name;}set{name = value;}}

    public DummySite(IComponent component){
        this.component = component;
        designSurface = new DesignSurface();
    }
    ~DummySite(){Dispose(false);}

    protected virtual void Dispose(bool isDisposing){
        if(isDisposing)
            designSurface.Dispose();
    }

    public void Dispose(){
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    public object GetService(Type serviceType){return designSurface.GetService(serviceType);}
}

static void GetComponents(IComponent component, int level, Action<IComponent, int> action){
    action(component, level);

    bool visible, enabled;
    Control control = component as Control;
    if(control != null){
        /*
         * Attaching the IDesigner sets the Visible and Enabled properties to true.
         * This is useful when you're designing your form in Visual Studio, but at
         * runtime, we'd rather the controls maintain their state, so we'll save the
         * values of these properties and restore them after we detach the IDesigner.
         */
        visible = control.Visible;
        enabled = control.Enabled;

        foreach(Control child in control.Controls)
            GetComponents(child, level + 1, action);
    }else visible = enabled = false;

    /*
     * The TypeDescriptor class has a handy static method that gets
     * the DesignerAttribute of the type of the component we pass it
     * and creates an instance of the IDesigner class for us.  This
     * saves us a lot of trouble.
     */
    ComponentDesigner des = TypeDescriptor.CreateDesigner(component, typeof(IDesigner)) as ComponentDesigner;
    if(des != null)
        try{
            DummySite site;
            if(component.Site == null)
                component.Site = site = new DummySite(component);
            else site = null;

            try{
                des.Initialize(component);
                foreach(IComponent child in des.AssociatedComponents)
                    GetComponents(child, level + 1, action);
            }finally{
                if(site != null){
                    component.Site = null;
                    site.Dispose();
                }
            }
        }finally{des.Dispose();}

    if(control != null){
        control.Visible = visible;
        control.Enabled = enabled;
    }
}


/* We'll use this in the ListComponents call */
[DllImport("user32.dll", CharSet=CharSet.Auto)]
static extern int SendMessage(IntPtr hWnd, int msg, int wParam, int lParam);

const int WM_SETREDRAW = 11;

void ListComponents(){
    /*
     * Invisible controls and disabled controls will be temporarily shown and enabled
     * during the GetComponents call (see the comment within that call), so to keep
     * them from showing up and then disappearing again (or appearing to temporarily
     * change enabled state), we'll disable redrawing of our window and re-enable it
     * afterwards.
     */
    SendMessage(Handle, WM_SETREDRAW, 0, 0);
    GetComponents(this, 0,
        /* You'll want to do something more useful here */
        (component, level)=>System.Diagnostics.Debug.WriteLine(new string('', level) + component));
    SendMessage(Handle, WM_SETREDRAW, 1, 0);
}