The Razor Framework :: Part 1 :: Plugins/Extensibility

/*****************************************************************
 * Module: EnumDescConverter.cs
 * Type: C# Source Code
 * Version: 1.0
 * Description: Enum Converter using Description Attributes
 * 
 * Revisions
 * ------------------------------------------------
 * [F] 24/02/2004, Jcl - Shaping up
 * [B] 25/02/2004, Jcl - Made it much easier :-)
 * 
 *****************************************************************/

/*
 * This code was gleamed from an excellent article from the code project by Javier Campos.
 * 
 * Thanks to his work, available here http://www.codeproject.com/csharp/EnumDescConverter.asp?print=true this
 * excellent class will become part of the framework.
 * */

using System;
using System.ComponentModel;
using System.Reflection;

namespace  Razor.Configuration
{
	/// <summary>
	/// EnumConverter supporting System.ComponentModel.DescriptionAttribute
	/// </summary>
	public class EnumDescConverter : System.ComponentModel.EnumConverter
	{
		protected System.Type _type;

		/// <summary>
		/// Initializes a new instance of the EnumDescConverter class
		/// </summary>
		/// <param name="type"></param>
		public EnumDescConverter(System.Type type) : base(type)
		{
			_type = type;
		}

		/// <summary>
		/// Overridden type conversion
		/// </summary>
		/// <param name="context"></param>
		/// <param name="culture"></param>
		/// <param name="value"></param>
		/// <param name="destinationType"></param>
		/// <returns></returns>
		public override object ConvertTo(ITypeDescriptorContext context, System.Globalization.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(_type, (string)value);
			}
			return base.ConvertTo (context, culture, value, destinationType);
		}

		/// <summary>
		/// Overridden type conversion
		/// </summary>
		/// <param name="context"></param>
		/// <param name="culture"></param>
		/// <param name="value"></param>
		/// <returns></returns>
		public override object ConvertFrom(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value)
		{
			if(value is string) 
			{
				return GetEnumValue(_type, (string)value);        
			}
			if(value is Enum) 
			{
				return GetEnumDescription((Enum)value);        
			}
			return base.ConvertFrom (context, culture, value);
		}

		/// <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)
		{
			FieldInfo fi= value.GetType().GetField(value.ToString()); 
			DescriptionAttribute[] attributes = (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
			return (attributes.Length>0)?attributes[0].Description:value.ToString();
		}
    
		/// <summary>
		/// Gets the description for certaing 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(System.Type value, string name)
		{
			FieldInfo fi= value.GetField(name); 
			DescriptionAttribute[] attributes = 
				(DescriptionAttribute[])fi.GetCustomAttributes(
				typeof(DescriptionAttribute), false);
			return (attributes.Length>0)?attributes[0].Description:name;
		}
    
		/// <summary>
		/// Returns the custom attributes from the Enum value specified
		/// </summary>
		/// <param name="enumType"></param>
		/// <param name="value"></param>
		/// <param name="attributeType"></param>
		/// <returns></returns>
		public static object[] GetEnumValueAttribute(Type enumType, Enum value, Type attributeType)
		{
			FieldInfo fi = enumType.GetField(value.ToString());
			return fi.GetCustomAttributes(attributeType, false);
		}

		/// <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(System.Type value, string description)
		{
			FieldInfo [] fis = value.GetFields();
			foreach(FieldInfo fi in fis) 
			{
				DescriptionAttribute[] 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;
		}
	}
}