Build enums (flags) in the designer of Visual Studio

Question

I have an enumeration of data types that can be displayed in a .NET Forms control, and I want to provide an interface for the control's users to filter some types (set some of the flags). The bit field seems to be a logical way to do this, unfortunately, the enumeration starts with 0, and not with 1 (0, 1, 2, 4, 8, ...) and cannot be changed.

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

Answer 1

UITypeEditor [EditorAttribute].

, - , , , , .

- - HashSet<T> - List<T>, .NET 2.0/3.0, .

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;
    }
}

Answer 2

: , . , . DesignTime, PropertyGrid Microsoft:

UITypeEditor, , . , UITypeEditor .

, , Marc. , , , , .

:

• (: MyFlags) (: MyProperty), .
• (: EnumEditorControl), .
• UITypeEditor (: EnumEditor); Editor. EnumEditorControl.
• TypeConverter (: EnumConverter); (TypeConverter) .

:

• Enum Flags.

  <Flags>
  Public Enum MyFlags
      Flag1 = 2 ^ 0
      Flag2 = 2 ^ 1
      Flag3 = 2 ^ 2
  End Enum
  

• .

  Public Property MyProperty() As MyFlags
      ...
  End Property
  

, (. # 6).

3. , .

   Imports System.Windows.Forms.Design
   Public Class EnumEditorControl(Of T As Structure)
       Public Sub New(value As Long, editorService As IWindowsFormsEditorService)
           'This call is required by the Windows.Forms Form Designer.
           InitializeComponent()
   
           _value = value
           _editorService = editorService
   
           For Each item As Long In [Enum].GetValues(GetType(T))
               Me.CheckedListBox1.Items.Add([Enum].GetName(GetType(T), item), (_value And item) = item)
           Next
   
       End Sub
   
       Private _value As Long
       Public Property Value As Long
           Get
               Return _value
           End Get
           Set(value As Long)
               _value = value
           End Set
       End Property
       Private _editorService As IWindowsFormsEditorService
   
       Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
           Dim v As Long = 0
           For Each item As String In Me.CheckedListBox1.CheckedItems
               v = (v Or [Enum].Parse(GetType(T), item))
           Next
           _value = v
           Me._editorService.CloseDropDown()
       End Sub
   End Class
   

designer.vb. : value editorService, ( ) " ", value ( ) , , Me._editorService.CloseDropDown().

4. UITypeEditor.

   Imports System.ComponentModel
   Imports System.Drawing.Design
   Imports System.Windows.Forms.Design
   
   Public Class EnumEditor(Of T As Structure)
       Inherits UITypeEditor
   
       Public Overrides Function GetEditStyle(context As ITypeDescriptorContext) As UITypeEditorEditStyle
           Return UITypeEditorEditStyle.DropDown
       End Function
       Public Overrides ReadOnly Property IsDropDownResizable() As Boolean
           Get
               Return True
           End Get
       End Property
       Public Overrides Function EditValue(context As ITypeDescriptorContext, provider As IServiceProvider, value As Object) As Object
           Dim svc As IWindowsFormsEditorService = DirectCast(provider.GetService(GetType(IWindowsFormsEditorService)), IWindowsFormsEditorService)
           Dim items As Long = CLng(value)
           If svc IsNot Nothing Then
               Dim c As New EnumEditorControl(Of T)(value, svc)
   
               svc.DropDownControl(c)
   
               value = c.Value
           End If
   
           Return CType(value, T)
       End Function
   End Class
   

- EditValue, (. # 3) svc.DropDownControl(c). , , .

5. TypeConverter, , .    System.ComponentModel    System.Drawing.Design    System.Text    System.Windows.Forms.Design

   Class EnumConverter(Of T As Structure)
       Inherits TypeConverter
   
       Public Overrides Function CanConvertTo(context As ITypeDescriptorContext, destinationType As Type) As Boolean
           Return destinationType = GetType(String) OrElse MyBase.CanConvertTo(context, destinationType)
       End Function
       Public Overrides Function ConvertTo(context As ITypeDescriptorContext, culture As System.Globalization.CultureInfo, value As Object, destinationType As Type) As Object
           If destinationType = GetType(String) Then
               Dim items As Integer = CLng(value)
   
               If items = 0 Then
                   Return ""
               End If
   
               Dim values As New List(Of String)
   
               For Each item As Integer In [Enum].GetValues(GetType(T))
                   If (items And item) = item Then
                       values.Add([Enum].GetName(GetType(T), item))
                   End If
               Next
               Return String.Join(", ", values)
           End If
   
           Return MyBase.ConvertTo(context, culture, value, destinationType)
       End Function
   End Class
   

6. , (. # 2).

   <Browsable(True),
   DefaultValue(MyFlags.Flag1),
   Editor(GetType(EnumEditor(Of MyFlags)), 
   GetType(System.Drawing.Design.UITypeEditor)),
   TypeConverter(GetType(EnumConverter(Of MyFlags)))
   >
   Public Property MyProperty() As MyFlags
       ...
   End Property
   

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