Expose a collection of enums (flags) in Visual Studio designer

I've got an enum of types of data that might be shown in a .NET Forms control and I want to provide an interface for consumers of the control to filter some of the types (set some of the flags). A bit field seems the logical way to do this, unfortunately, the enum starts at 0 rather than 1 (0, 1, 2, 4, 8, ...) and can't be changed.

How can I expose this set of flags so that it can be easily configured programmatically or through the Visual Studio designer?

From stackoverflow

• You would need to write a UITypeEditor to do the work, and associate it with the property via [EditorAttribute].

  edit now with example - a fairly long one, I'm afraid - but most of the code can be shared between types, fortunately.

  You can't use a single composite enum value because of the zero - so here I'm using a HashSet<T> to hold the selected enums - fairly easy to re-work to List<T> if you have .NET 2.0/3.0, though.

  using System;
  using System.Collections.Generic;
  using System.ComponentModel;
  using System.Drawing.Design;
  using System.Text;
  using System.Windows.Forms;
  using System.Windows.Forms.Design;
  
  public class MyControl : UserControl
  {
      public MyControl()
      {
          Values = new HashSet<MyEnum>();
      }
      [Editor(typeof(MyEnumSetEditor), typeof(UITypeEditor))]
      [TypeConverter(typeof(MyEnumSetConverter))]
      public HashSet<MyEnum> Values { get; set; }
  }
  
  public enum MyEnum
  {  // numbers as per the question...
      A = 0, B = 1, C = 2, D = 4, E = 8
  }
  class MyEnumSetEditor : EnumSetEditor<MyEnum> { }
  class MyEnumSetConverter : EnumSetConverter<MyEnum> { }
  
  // from here down is shared between types
  abstract class EnumSetConverter<T> : TypeConverter where T : struct
  {
      public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
      {
          return destinationType == typeof(string) || base.CanConvertTo(context, destinationType);
      }
      public override object ConvertTo(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value, Type destinationType)
      {
          if(destinationType == typeof(string))
          {
              HashSet<T> set = (HashSet<T>)value;
              if (set == null) return "(null)";
  
              StringBuilder sb = new StringBuilder();
              foreach (T item in Enum.GetValues(typeof(T)))
              {
                  if (set.Contains(item))
                  {
                      if (sb.Length > 0) sb.Append(", ");
                      sb.Append(item);
                  }
              }
              return sb.ToString();
          }
          return base.ConvertTo(context, culture, value, destinationType);
      }
  }
  
  public abstract class EnumSetEditor<T> : UITypeEditor where T : struct
  {
      public override UITypeEditorEditStyle GetEditStyle(ITypeDescriptorContext context)
      {
          return UITypeEditorEditStyle.DropDown;
      }
      public override bool IsDropDownResizable
      {
          get { return true; }
      }
      public override object EditValue(ITypeDescriptorContext context, IServiceProvider provider, object value)
      {
          IWindowsFormsEditorService svc = (IWindowsFormsEditorService)
              provider.GetService(typeof(IWindowsFormsEditorService));
          HashSet<T> set = value as HashSet<T>;
          if (svc != null && set != null)
          {
              UserControl ctrl = new UserControl();
              CheckedListBox clb = new CheckedListBox();
              clb.Dock = DockStyle.Fill;
              Button btn = new Button();
              btn.Dock = DockStyle.Bottom;
              foreach (T item in Enum.GetValues(typeof(T)))
              {
                  clb.Items.Add(item, set.Contains(item));
              }
              ctrl.Controls.Add(clb);
              ctrl.Controls.Add(btn);
              btn.Text = "OK";
              btn.Click += delegate
              {
                  set.Clear();
                  foreach (T item in clb.CheckedItems)
                  {
                      set.Add(item);
                  }
                  svc.CloseDropDown();
              };
              svc.DropDownControl(ctrl);
          }
  
          return value;
      }
  }
  

  dmo : Wow. Marc - I really appreciate you taking the time to do this.