C#

ArjenGroeneveld wrote:

like to create a Label control

public class LabelExtended : System.Windows.Forms.Label
{
   ...
}

ArjenGroeneveld wrote:

One the respective control is set in Design time,

private string selectedControlName = string.Empty;

[
CategoryAttribute("Arjens Properties"),
DescriptionAttribute("Holds the name of the selected control."),
DefaultValueAttribute(""),
EditorAttribute(typeof(SelectControlEditor), typeof(UITypeEditor)) // this is the key
]
public string SelectedControlName
{
    get { return selectedControlName; }
    set { selectedControlName = value; }
}

ArjenGroeneveld wrote:

an property in which I can select the available controls on the Form (except for the Label controls).

using System;
using System.Windows.Forms;
using System.Windows.Forms.Design;
using System.ComponentModel;
using System.Drawing.Design;
...
    public class SelectControlEditor : UITypeEditor
    {
        ...
    }

public override UITypeEditorEditStyle GetEditStyle(ITypeDescriptorContext context)
{
    if( context != null ) return UITypeEditorEditStyle.DropDown;
    return base.GetEditStyle(context);
}

public override object EditValue(ITypeDescriptorContext context, IServiceProvider provider, object value)
{
    if ((context != null) && (provider != null))
    {
        // Access the Property Browser's UI display service
        IWindowsFormsEditorService editorService = (IWindowsFormsEditorService)provider.GetService(typeof(IWindowsFormsEditorService));

        if (editorService != null)
        {
            Control owner = context.Instance as Control; // get the control which is the owner of your property
            if (owner != null)
            {
                // Create an instance of the UI editor control
                SelectControl selectControlEditor = new SelectControl(editorService, owner); // your CustomControl which is shown in the designer (will be descriped next)

                // Pass the UI editor control the current property value
                selectControlEditor.SelectedControl = (string)value;

                // Display the UI editor control
                editorService.DropDownControl(selectControlEditor);

                // Return the new property value from the UI editor control (over the SelectedControl property),
                // but only if the Valid property if the custom control is set to true!
                // Else return the old value.
                if (selectControlEditor.Valid)
                {
                    return selectControlEditor.SelectedControl;
                }
                else
                {
                    return value;
                }
            }
        }
    }
    return base.EditValue(context, provider, value);
}

public partial class SelectControl : UserControl
{
    IWindowsFormsEditorService editorService = null;

    public SelectControl(IWindowsFormsEditorService editorService, Control ownerControl)
    {
        InitializeComponent();

        this.editorService = editorService;
        if (ownerControl != null)
        {
            // get parent Control of the properties owner control.
            Control parentControl = ownerControl.Parent;
            if (parentControl != null)
            {
                // iterate over all controls in the parentControl Collection
                foreach (Control c in parentControl.Controls)
                {
                    // if the control is not of the type LabelExtended
                    if (!c is LabelExtended)
                    {
                        // add the name to the Items Collection of the combobox.
                        cbSelectControls.Items.Add(c.Name);
                    }
                }
            }
        }
    }

    // is set initial by the UITypeEditor,
    // and holds the selected Text from the combobox.
    public string SelectedControl
    {
        get { return cbSelectControls.Text; }
        set { cbSelectControls.Text = value;}
    }

    bool valid = false;
    // default set to false.
    // only true if the ok button was clicked.
    public bool Valid
    {
        get { return valid; }
        set { valid = value; }
    }
 
    // click event sets Valid to true and closes the dropdown. (finish edit of the property)
    private void bOk_Click(object sender, EventArgs e)
    {
        Valid = true;
        editorService.CloseDropDown();
    }
}

ArjenGroeneveld wrote:

this control will get the focus in Runtime when the user moves with the mouse over the Label control

protected override void OnMouseEnter(EventArgs e)
{
    // not in DesignMode
    if (!DesignMode)
    {
        // only if the is a valid control name set
        if (!string.IsNullOrEmpty(SelectedControlName))
        {
            Control parentControl = this.Parent;
            if (parentControl != null)
            {
                // you know this from the code above ...
                foreach (Control c in parentControl.Controls)
                {
                    // if the actual controls name is equal to the slected name
                    if (c.Name.Equals(SelectedControlName))
                    {
                        c.Focus();  // set Focus!
                    }
                }
            }
        }
    }
    base.OnMouseEnter(e);
}