class/System.ComponentModel.DataAnnotations/System.ComponentModel.DataAnnotations/EnumDataTypeAttribute.cs

   1 //
   2 // EnumDataTypeAttribute.cs
   3 //
   4 // Authors:
   5 //      Marek Habersack <mhabersack@novell.com>
   6 //
   7 // Copyright (C) 2010 Novell Inc. (http://novell.com)
   8 //
   9
  10 //
  11 // Permission is hereby granted, free of charge, to any person obtaining
  12 // a copy of this software and associated documentation files (the
  13 // "Software"), to deal in the Software without restriction, including
  14 // without limitation the rights to use, copy, modify, merge, publish,
  15 // distribute, sublicense, and/or sell copies of the Software, and to
  16 // permit persons to whom the Software is furnished to do so, subject to
  17 // the following conditions:
  18 //
  19 // The above copyright notice and this permission notice shall be
  20 // included in all copies or substantial portions of the Software.
  21 //
  22 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  23 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  24 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  25 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  26 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  27 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  28 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  29 //
  30 #if NET_4_0
  31 using System;
  32 using System.Collections.Generic;
  33 using System.ComponentModel;
  34 using System.Globalization;
  35
  36 namespace System.ComponentModel.DataAnnotations
  37 {
  38         [AttributeUsage (AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]
  39         public sealed class EnumDataTypeAttribute : DataTypeAttribute
  40         {
  41                 public Type EnumType { get; private set; }
  42
  43                 public EnumDataTypeAttribute (Type enumType)
  44                         : base (DataType.Custom)
  45                 {
  46                         this.EnumType = enumType;
  47                 }
  48
  49                 public override bool IsValid (object value)
  50                 {
  51                         Type type = EnumType;
  52
  53                         if (!type.IsEnum)
  54                                 throw new InvalidOperationException (
  55                                         String.Format ("The type '{0}' needs to represent an enumeration type.", type.FullName)
  56                                 );
  57
  58                         if (value == null)
  59                                 return true;
  60
  61                         Type valueType = value.GetType ();
  62                         if (valueType.IsEnum && valueType != type)
  63                                 return false;
  64
  65                         string s = value as string;
  66                         if (s != null && s.Length == 0)
  67                                 return true;
  68
  69                         if (s != null && (valueType == typeof (bool) || valueType == typeof (char) || valueType == typeof (float)))
  70                                 return false;
  71
  72                         object o;
  73
  74                         if (s != null) {
  75                                 try {
  76                                         o = Enum.Parse (type, s);
  77                                 } catch {
  78                                         return false;
  79                                 }
  80                         } else if (valueType.IsEnum)
  81                                 o = value;
  82                         else {
  83                                 try {
  84                                         o = Enum.ToObject (type, value);
  85                                 } catch {
  86                                         return false;
  87                                 }
  88                         }
  89
  90                         object[] attrs = type.GetCustomAttributes (typeof (FlagsAttribute), true);
  91                         if (attrs != null && attrs.Length > 0) {
  92                                 string sval = Convert.ChangeType (o, Enum.GetUnderlyingType (type), CultureInfo.InvariantCulture).ToString ();
  93
  94                                 // This looks weird, but what happens here is that if we have a
  95                                 // mismatch, the above type change will make sval equal o.ToString
  96                                 // () and if we have a match, then sval will be string
  97                                 // representation of the enum member's value. So, if we have an
  98                                 // enum:
  99                                 //
 100                                 // [Flags]
 101                                 // enum Test
 102                                 // {
 103                                 //     One = 1,
 104                                 //     Two = 2
 105                                 // }
 106                                 //
 107                                 // And the passed value was 3, then o.ToString () == "One, Two" and
 108                                 // sval == "3". If the passed value was 33, though, o.ToString () ==
 109                                 // "33" and sval == "33" - thus we DON'T have a match.
 110                                 return !sval.Equals (o.ToString ());
 111                         }
 112
 113                         return Enum.IsDefined (type, o);
 114                 }
 115         }
 116 }
 117 #endif