mcs/class/corlib/System/Nullable.cs

   1 //
   2 // System.Nullable
   3 //
   4 // Martin Baulig (martin@ximian.com)
   5 //
   6 // (C) 2004 Novell, Inc.
   7 //
   8
   9 //
  10 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
  11 //
  12 // Permission is hereby granted, free of charge, to any person obtaining
  13 // a copy of this software and associated documentation files (the
  14 // "Software"), to deal in the Software without restriction, including
  15 // without limitation the rights to use, copy, modify, merge, publish,
  16 // distribute, sublicense, and/or sell copies of the Software, and to
  17 // permit persons to whom the Software is furnished to do so, subject to
  18 // the following conditions:
  19 //
  20 // The above copyright notice and this permission notice shall be
  21 // included in all copies or substantial portions of the Software.
  22 //
  23 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  27 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  28 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  29 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  30 //
  31
  32 using System.Reflection;
  33 #if NET_2_0
  34 using System.Collections.Generic;
  35 #endif
  36 using System.Runtime.CompilerServices;
  37
  38 #if NET_2_0
  39 namespace System
  40 {
  41
  42         [CLSCompliant(false)]
  43         public static class Nullable
  44         {
  45                 public static int Compare<T> (Nullable<T> left, Nullable<T> right)
  46                 {
  47                         IComparable icomparable = left.value as IComparable;
  48                         if (icomparable == null)
  49                                 throw new ArgumentException ("At least one object must implement IComparable.");
  50                         if (left.has_value == false && right.has_value == false)
  51                                 return 0;
  52                         if (!left.has_value)
  53                                 return -1;
  54                         if (!right.has_value)
  55                                 return 1;
  56
  57                         return icomparable.CompareTo (right.value);
  58                 }
  59
  60                 public static bool Equals<T> (Nullable <T> value1, Nullable<T> value2)
  61                 {
  62                         return value1.Equals (value2);
  63                 }
  64
  65                 public static Nullable<T> FromObject<T> (object value)
  66                 {
  67                         if (!(value is T))
  68                                 throw new ArgumentException ("Object type can not be converted to target type.");
  69
  70                         return new Nullable<T> ((T) value);
  71                 }
  72
  73                 public static T GetValueOrDefault<T>(Nullable<T> value)
  74                 {
  75                         return GetValueOrDefault<T> (value, default (T));
  76                 }
  77
  78                 public static T GetValueOrDefault<T> (Nullable<T> value, T defaultValue)
  79                 {
  80                         if (!value.has_value)
  81                                 return defaultValue;
  82
  83                         return value.value;
  84                 }
  85
  86                 public static bool HasValue<T> (Nullable <T> value)
  87                 {
  88                         return value.has_value;
  89                 }
  90
  91                 public static object ToObject<T> (Nullable<T> value)
  92                 {
  93                         if (!value.has_value)
  94                                 return null;
  95
  96                         return (object)value.value;
  97                 }
  98         }
  99
 100         [CLSCompliant(false)]
 101         public struct Nullable<T> : IComparable, INullableValue
 102         {
 103                 internal T value;
 104                 internal bool has_value;
 105
 106                 public Nullable (T value)
 107                 {
 108                         if (value == null)
 109                                 this.has_value = false;
 110                         else
 111                                 this.has_value = true;
 112
 113                         this.value = value;
 114                 }
 115
 116                 public bool HasValue {
 117                         get { return has_value; }
 118                 }
 119
 120                 public T Value {
 121                         get {
 122                                 if (!has_value)
 123                                         throw new InvalidOperationException ("Nullable object must have a value.");
 124
 125                                 return value;
 126                         }
 127                 }
 128
 129                 object INullableValue.Value {
 130                         get {
 131                                 return (object)Value;
 132                         }
 133                 }
 134
 135                 [Obsolete]
 136                 public int CompareTo (Nullable<T> other)
 137                 {
 138                         return Nullable.Compare<T> (this, other);
 139                 }
 140
 141                 [Obsolete]
 142                 public int CompareTo (object other)
 143                 {
 144                         if (!(other is Nullable<T>))
 145                                 throw new ArgumentException ("Object type can not be converted to target type.");
 146
 147                         return Nullable.Compare<T> (this, (Nullable<T>) other);
 148                 }
 149
 150                 public override bool Equals (object other)
 151                 {
 152                         if (!(other is Nullable<T>))
 153                                 return false;
 154
 155                         return Equals ((Nullable <T>) other);
 156                 }
 157
 158                 public bool Equals (Nullable<T> other)
 159                 {
 160                         if (other.has_value != has_value)
 161                                 return false;
 162
 163                         if (has_value == false)
 164                                 return true;
 165
 166                         return other.value.Equals (value);
 167                 }
 168
 169                 [Obsolete]
 170                 public static Nullable<T> FromObject (object value)
 171                 {
 172                         return Nullable.FromObject<T> (value);
 173                 }
 174
 175                 public override int GetHashCode ()
 176                 {
 177                         if (!has_value)
 178                                 return 0;
 179
 180                         return value.GetHashCode ();
 181                 }
 182
 183                 [Obsolete]
 184                 public T GetValueOrDefault ()
 185                 {
 186                         return Nullable.GetValueOrDefault<T> (this, default (T));
 187                 }
 188
 189                 [Obsolete]
 190                 public T GetValueOrDefault (T def_value)
 191                 {
 192                         return Nullable.GetValueOrDefault<T> (this, def_value);
 193                 }
 194
 195                 public object ToObject ()
 196                 {
 197                         if (!has_value)
 198                                 return null;
 199
 200                         return (object)value;
 201                 }
 202
 203                 public override string ToString ()
 204                 {
 205                         if (has_value)
 206                                 return value.ToString ();
 207                         else
 208                                 return "";
 209                 }
 210
 211                 public static implicit operator Nullable<T> (T value)
 212                 {
 213                         return new Nullable<T> (value);
 214                 }
 215
 216                 public static explicit operator T (Nullable<T> value)
 217                 {
 218                         return value.Value;
 219                 }
 220
 221                 public static bool operator == (Nullable<T> left, Nullable<T> right)
 222                 {
 223                         return left.Equals (right);
 224                 }
 225
 226                 public static bool operator != (Nullable<T> left, Nullable<T> right)
 227                 {
 228                         return !left.Equals (right);
 229                 }
 230         }
 231 }
 232 #endif