MetaEnumSelectionAttribute.cs

    using System;
    using System.Web.Mvc;

    using EPiServer.Shell.ObjectEditing;

    using Mediachase.BusinessFoundation.Data.Meta.Management;

    /// <summary>
    /// The meta enum selection attribute.
    /// </summary>
    [AttributeUsage(AttributeTargets.Property)]
    public sealed class MetaEnumSelectionAttribute : SelectManyAttribute, IMetadataAware
    {
        /// <summary>
        /// Gets the name of the <see cref="McDataType" />.
        /// </summary>
        /// <value>The name of the mc data type.</value>
        public string McDataTypeName { get; }

        /// <summary>
        /// Initializes a new instance of the <see cref="MetaEnumSelectionAttribute"/> class.
        /// </summary>
        /// <param name="mcDataTypeName">Name of the <see cref="McDataType" />.</param>
        public MetaEnumSelectionAttribute(string mcDataTypeName)
        {
            this.McDataTypeName = mcDataTypeName;
        }

        /// <summary>
        /// Called when [metadata created].
        /// </summary>
        /// <param name="metadata">
        /// The metadata.
        /// </param>
        public new void OnMetadataCreated(ModelMetadata metadata)
        {
            if (metadata == null)
            {
                return;
            }

            this.SelectionFactoryType = typeof(MetaEnumSelectionFactory);

            base.OnMetadataCreated(metadata);
        }
    }

MetaEnumSelectionFactory.cs

    using System;
    using System.Collections.Generic;
    using System.Linq;

    using EPiServer.Logging;
    using EPiServer.Shell.ObjectEditing;

    using Mediachase.BusinessFoundation.Data;
    using Mediachase.BusinessFoundation.Data.Meta;
    using Mediachase.BusinessFoundation.Data.Meta.Management;

    /// <summary>
    /// Class MetaEnumSelectionFactory.
    /// </summary>
    /// <seealso cref="EPiServer.Shell.ObjectEditing.ISelectionFactory" />
    public class MetaEnumSelectionFactory : ISelectionFactory
    {
        /// <summary>
        /// The log.
        /// </summary>
        private static readonly ILogger Log = LogManager.GetLogger();

        /// <summary>
        /// Creates a list of selection items for a specific property.
        /// </summary>
        /// <param name="metadata">
        /// The metadata for a property.
        /// </param>
        /// <returns>
        /// A list of selection items for a specific property.
        /// </returns>
        public IEnumerable<ISelectItem> GetSelections(ExtendedMetadata metadata)
        {
            try
            {
                MetaEnumSelectionAttribute metaEnumSelectionAttribute =
                    metadata.Attributes.OfType<MetaEnumSelectionAttribute>().SingleOrDefault();

                MetaFieldType currentType = null;

                if (metaEnumSelectionAttribute != null
                    && !string.IsNullOrEmpty(metaEnumSelectionAttribute.McDataTypeName))
                {
                    currentType =
                        DataContext.Current.MetaModel.RegisteredTypes.Cast<MetaFieldType>()
                            .FirstOrDefault(
                                type =>
                                type.McDataType == McDataType.Enum
                                && type.Name.Equals(
                                    metaEnumSelectionAttribute.McDataTypeName, 
                                    StringComparison.OrdinalIgnoreCase));
                }

                if (currentType == null)
                {
                    return new List<ISelectItem>();
                }

                MetaEnumItem[] values = MetaEnum.GetItems(currentType);

                return
                    values.Select(
                        metaEnumItem =>
                        new SelectItem
                            {
                                Text = MetaEnum.GetFriendlyName(currentType, metaEnumItem.Handle), 
                                Value = metaEnumItem.Handle.ToString()
                            }).Cast<ISelectItem>().ToList();
            }
            catch (ArgumentNullException argumentNullException)
            {
                Log.Error(argumentNullException.Message, argumentNullException);
            }
            catch (ArgumentException argumentException)
            {
                Log.Error(argumentException.Message, argumentException);
            }
            catch (InvalidOperationException invalidOperationException)
            {
                Log.Error(invalidOperationException.Message, invalidOperationException);
            }
            catch (InvalidCastException invalidCastException)
            {
                Log.Error(invalidCastException.Message, invalidCastException);
            }

            return new List<ISelectItem>();
        }
    }

Usage.txt

[MetaEnumSelection("ContactGroup")]
public virtual string Customergroups { get; set; }