Un simple TypeConverter junto a un UITypeEditor (opcional) para representar un color en formato web.



Nota: los colores no se ven como deberían por la compresión de imagen del software que he usado para capturar el GIF animado xD

WebColorConverter.vb

#Region " Option Statements "
 
Option Strict On
Option Explicit On
Option Infer Off
 
#End Region
 
#Region " Imports "
 
Imports System.ComponentModel
Imports System.Globalization
 
#End Region
 
Public Class WebColorConverter : Inherits ColorConverter
 
    <DebuggerStepThrough>
    Public Overrides Function GetStandardValuesSupported(context As ITypeDescriptorContext) As Boolean
 
        Return True
    End Function
 
    <DebuggerStepThrough>
    Public Overrides Function GetStandardValues(context As ITypeDescriptorContext) As StandardValuesCollection
 
        Dim collection As New Collection()
 
        For Each kc As KnownColor In [Enum].GetValues(GetType(KnownColor))
            Dim color As Color = Color.FromKnownColor(kc)
 
            If Not color.IsSystemColor AndAlso color.IsNamedColor Then
                collection.Add(color)
            End If
        Next
 
        Return New StandardValuesCollection(collection)
    End Function
 
    <DebuggerStepThrough>
    Public Overrides Function ConvertTo(context As ITypeDescriptorContext,
                                    culture As CultureInfo,
                                    value As Object,
                                    destinationType As Type) As Object
 
        If destinationType Is GetType(String) AndAlso TypeOf value Is Color Then
            Dim color As Color = DirectCast(value, Color)
            Dim html As String = If(color.A <> 255, $"#{color.A:X2}{color.R:X2}{color.G:X2}{color.B:X2}",
                                    ColorTranslator.ToHtml(Color.FromArgb(color.R, color.G, color.B)))
 
            Dim name As String = Nothing
            For Each knownColor As KnownColor In [Enum].GetValues(GetType(KnownColor))
                Dim k As Color = Color.FromKnownColor(knownColor)
                If k.A = color.A AndAlso
                   k.R = color.R AndAlso
                   k.G = color.G AndAlso
                   k.B = color.B AndAlso Not k.IsSystemColor Then
 
                    name = k.Name
                    Exit For
                End If
            Next
 
            Return If(name IsNot Nothing, $"{html} ({name})", html)
        End If
 
        Return MyBase.ConvertTo(context, culture, value, destinationType)
    End Function
 
    <DebuggerStepThrough>
    Public Overrides Function ConvertFrom(context As ITypeDescriptorContext,
                                          culture As CultureInfo,
                                          value As Object) As Object
 
        Dim s As String = TryCast(value, String)
        If s IsNot Nothing Then
            s = s.Trim()
 
            ' If input is like "xxx (Name)" remove the part in parentheses
            Dim idx As Integer = s.IndexOf("("c)
            If idx >= 0 Then
                s = s.Substring(0, idx).Trim()
            End If
 
            If s.StartsWith("#") Then
                Dim hx As String = s.Substring(1).Trim()
 
                ' Support #RRGGBB and #AARRGGBB
                If hx.Length = 6 Then
                    Dim r As Integer = Convert.ToInt32(hx.Substring(0, 2), 16)
                    Dim g As Integer = Convert.ToInt32(hx.Substring(2, 2), 16)
                    Dim b As Integer = Convert.ToInt32(hx.Substring(4, 2), 16)
                    Return Color.FromArgb(255, r, g, b)
 
                ElseIf hx.Length = 8 Then
                    Dim a As Integer = Convert.ToInt32(hx.Substring(0, 2), 16)
                    Dim r As Integer = Convert.ToInt32(hx.Substring(2, 2), 16)
                    Dim g As Integer = Convert.ToInt32(hx.Substring(4, 2), 16)
                    Dim b As Integer = Convert.ToInt32(hx.Substring(6, 2), 16)
                    Return Color.FromArgb(a, r, g, b)
 
                Else
                    ' Support short hex format (#RGB) by expanding to 6 digits
                    If hx.Length = 3 Then
                        Dim r As Integer = Convert.ToInt32(String.Concat(hx(0), hx(0)), 16)
                        Dim g As Integer = Convert.ToInt32(String.Concat(hx(1), hx(1)), 16)
                        Dim b As Integer = Convert.ToInt32(String.Concat(hx(2), hx(2)), 16)
                        Return Color.FromArgb(255, r, g, b)
                    End If
                End If
 
            Else
                ' Try ColorTranslator for standard names and "Transparent"
                Try
                    Dim c As Color = ColorTranslator.FromHtml(s)
                    ' ColorTranslator.FromHtml returns A=255 for known names; A=0 for "Transparent"
                    Return c
 
                Catch ex As Exception
                    ' Try KnownColor enum (e.g. user types "White" or "WhiteSmoke")
                    Try
                        Dim kc As KnownColor
                        If [Enum].TryParse(s, True, kc) Then
                            Return Color.FromKnownColor(kc)
                        End If
                    Catch
                        ' Continue to fallback
                    End Try
                End Try
            End If
 
            ' If everything fails, fallback to the base converter (throws or defaults)
        End If
 
        Return MyBase.ConvertFrom(context, culture, value)
    End Function
 
End Class
 

WebColorEditor.vb

#Region " Option Statements "
 
Option Strict On
Option Explicit On
Option Infer Off
 
#End Region
 
#Region " Imports "
 
Imports System.ComponentModel
Imports System.Drawing.Design
 
#End Region
 
Public Class WebColorEditor : Inherits UITypeEditor
 
    <DebuggerStepThrough>
    Public Overrides Function GetEditStyle(context As ITypeDescriptorContext) As UITypeEditorEditStyle
 
        Return UITypeEditorEditStyle.None
    End Function
 
    <DebuggerStepThrough>
    Public Overrides Function GetPaintValueSupported(context As ITypeDescriptorContext) As Boolean
 
        Return True
    End Function
 
    <DebuggerStepThrough>
    Public Overrides Sub PaintValue(e As PaintValueEventArgs)
 
        Dim color As Color
 
        If TypeOf e.Value Is Color Then
            color = DirectCast(e.Value, Color)
        Else
            Exit Sub
        End If
 
        Using brush As New SolidBrush(color)
            e.Graphics.FillRectangle(brush, e.Bounds)
        End Using
    End Sub
 
End Class

Modo de empleo:

Imports System.ComponentModel
Imports System.Drawing.Design
 
Public Class Form1
 
    Private ReadOnly ClassTest As New MyClassTest
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
 
        Me.PropertyGrid1.SelectedObject = Me.ClassTest
    End Sub
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
 
        Me.ClassTest.MyColor = Color.FromArgb(255, 116, 222, 4)
        Me.PropertyGrid1.Refresh()
    End Sub
End Class
 
Friend NotInheritable Class MyClassTest
 
    <TypeConverter(GetType(WebColorConverter))>
    <Editor(GetType(WebColorEditor), GetType(UITypeEditor))> ' El editor es opcional.
    Public Property MyColor As Color = Color.Transparent
 
End Class

Ejemplo de utilidad en la vida real: un programa open-source para mostrar en tiempo real el color del pixel actual en la pantalla (entre otras cosas):