Zeta Enterprise Library

namespace Zeta.EnterpriseLibrary.Tools
{
	using System;
	using System.ComponentModel;
	using System.Globalization;
	using System.Reflection;

	/// <summary>
	/// EnumConverter supporting System.ComponentModel.DescriptionAttribute
	/// </summary>
	public class EnumDescriptionConverter : EnumConverter
	{
		private readonly Type _myVal;

		/// <summary>
		/// Initializes a new instance of the <see cref="EnumDescriptionConverter"/> class.
		/// </summary>
		/// <param name="type">A <see cref="T:System.Type"/> that represents the type of enumeration to associate with this enumeration converter.</param>
		public EnumDescriptionConverter( Type type )
			: base( type )
		{
			_myVal = type;
		}

		/// <summary>
		/// Gets Enum Value's Description Attribute
		/// </summary>
		/// <param name="value">The value you want the description attribute for</param>
		/// <returns>The description, if any, else it's .ToString()</returns>
		public static string GetEnumDescription( Enum value )
		{
			var fi = value.GetType().GetField( value.ToString() );
			var attributes =
				(DescriptionAttribute[])fi.GetCustomAttributes(
											 typeof( DescriptionAttribute ), false );
			return (attributes.Length > 0) ? attributes[0].Description : value.ToString();
		}

		/// <summary>
		/// Gets the description for a certain named value in an Enumeration
		/// </summary>
		/// <param name="value">The type of the Enumeration</param>
		/// <param name="name">The name of the Enumeration value</param>
		/// <returns>The description, if any, else the passed name</returns>
		public static string GetEnumDescription( Type value, string name )
		{
			var fi = value.GetField( name );
			var attributes =
				(DescriptionAttribute[])fi.GetCustomAttributes(
											 typeof( DescriptionAttribute ), false );
			return (attributes.Length > 0) ? attributes[0].Description : name;
		}

		/// <summary>
		/// Gets the value of an Enum, based on it's Description Attribute or named value
		/// </summary>
		/// <param name="value">The Enum type</param>
		/// <param name="description">The description or name of the element</param>
		/// <returns>The value, or the passed in description, if it was not found</returns>
		public static object GetEnumValue( Type value, string description )
		{
			FieldInfo[] fis = value.GetFields();
			foreach ( FieldInfo fi in fis )
			{
				var attributes =
					(DescriptionAttribute[])fi.GetCustomAttributes(
												 typeof( DescriptionAttribute ), false );
				if ( attributes.Length > 0 )
				{
					if ( attributes[0].Description == description )
					{
						return fi.GetValue( fi.Name );
					}
				}
				if ( fi.Name == description )
				{
					return fi.GetValue( fi.Name );
				}
			}
			return description;
		}


		/// <summary>
		/// Determines whether this instance [can convert from] the specified context.
		/// </summary>
		/// <param name="context">The context.</param>
		/// <param name="sourceType">Type of the source.</param>
		/// <returns>
		/// 	<c>true</c> if this instance [can convert from] the specified context; otherwise, <c>false</c>.
		/// </returns>
		public override bool CanConvertFrom( ITypeDescriptorContext context, Type sourceType )
		{
			return sourceType == typeof( Enum ) || base.CanConvertFrom( context, sourceType );
		}

		/// <summary>
		/// Determines whether this instance [can convert to] the specified context.
		/// </summary>
		/// <param name="context">The context.</param>
		/// <param name="destinationType">Type of the destination.</param>
		/// <returns>
		/// 	<c>true</c> if this instance [can convert to] the specified context; otherwise, <c>false</c>.
		/// </returns>
		public override bool CanConvertTo( ITypeDescriptorContext context, Type destinationType )
		{
			return destinationType == typeof( string ) || base.CanConvertTo( context, destinationType );
		}

		/// <summary>
		/// Converts to.
		/// </summary>
		/// <param name="context">The context.</param>
		/// <param name="culture">The culture.</param>
		/// <param name="value">The value.</param>
		/// <param name="destinationType">Type of the destination.</param>
		/// <returns></returns>
		public override object ConvertTo( ITypeDescriptorContext context, CultureInfo culture, object value,
										 Type destinationType )
		{
			if ( value is Enum && destinationType == typeof( string ) )
			{
				return GetEnumDescription( (Enum)value );
			}
			if ( value is string && destinationType == typeof( string ) )
			{
				return GetEnumDescription( _myVal, (string)value );
			}
			return base.ConvertTo( context, culture, value, destinationType );
		}

		/// <summary>
		/// Converts from.
		/// </summary>
		/// <param name="context">The context.</param>
		/// <param name="culture">The culture.</param>
		/// <param name="value">The value.</param>
		/// <returns></returns>
		public override object ConvertFrom( 
			ITypeDescriptorContext context, 
			CultureInfo culture, 
			object value )
		{
			if ( value is string )
			{
				return GetEnumValue( _myVal, (string)value );
			}
			if ( value is Enum )
			{
				return GetEnumValue( _myVal, value.ToString() );
			}
			return base.ConvertFrom( context, culture, value );
		}
	}
}