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         public static class Nullable {
  41                 public static int Compare<T> (Nullable<T> left, Nullable<T> right)
  42                 {
  43                         IComparable icomparable = left.value as IComparable;
  44                         if (icomparable == null)
  45                                 throw new ArgumentException ("At least one object must implement IComparable.");
  46                         if (left.has_value == false && right.has_value == false)
  47                                 return 0;
  48                         if (!left.has_value)
  49                                 return -1;
  50                         if (!right.has_value)
  51                                 return 1;
  52
  53                         return icomparable.CompareTo (right.value);
  54                 }
  55
  56                 public static bool Equals<T> (Nullable <T> value1, Nullable<T> value2)
  57                 {
  58                         return value1.Equals (value2);
  59                 }
  60
  61                 public static Nullable<T> FromObject<T> (object value)
  62                 {
  63                         if (!(value is T))
  64                                 throw new ArgumentException ("Object type can not be converted to target type.");
  65
  66                         return new Nullable<T> ((T) value);
  67                 }
  68
  69                 public static T GetValueOrDefault<T>(Nullable<T> value)
  70                 {
  71                         return GetValueOrDefault<T> (value, default (T));
  72                 }
  73
  74                 public static T GetValueOrDefault<T> (Nullable<T> value, T defaultValue)
  75                 {
  76                         if (!value.has_value)
  77                                 return defaultValue;
  78
  79                         return value.value;
  80                 }
  81
  82                 public static bool HasValue<T> (Nullable <T> value)
  83                 {
  84                         return value.has_value;
  85                 }
  86
  87                 public static object ToObject<T> (Nullable<T> value)
  88                 {
  89                         if (!value.has_value)
  90                                 return null;
  91
  92                         return (object)value.value;
  93                 }
  94         }
  95
  96         public struct Nullable<T> : IComparable, INullableValue
  97         {
  98                 internal T value;
  99                 internal bool has_value;
 100
 101                 public Nullable (T value)
 102                 {
 103                         if (value == null)
 104                                 this.has_value = false;
 105                         else
 106                                 this.has_value = true;
 107
 108                         this.value = value;
 109                 }
 110
 111                 public bool HasValue {
 112                         get { return has_value; }
 113                 }
 114
 115                 public T Value {
 116                         get {
 117                                 if (!has_value)
 118                                         throw new InvalidOperationException ("Nullable object must have a value.");
 119
 120                                 return value;
 121                         }
 122                 }
 123
 124                 object INullableValue.Value {
 125                         get {
 126                                 return (object)Value;
 127                         }
 128                 }
 129
 130                 [Obsolete]
 131                 public int CompareTo (Nullable<T> other)
 132                 {
 133                         return Nullable.Compare<T> (this, other);
 134                 }
 135
 136                 [Obsolete]
 137                 public int CompareTo (object other)
 138                 {
 139                         if (!(other is Nullable<T>))
 140                                 throw new ArgumentException ("Object type can not be converted to target type.");
 141
 142                         return Nullable.Compare<T> (this, (Nullable<T>) other);
 143                 }
 144
 145                 public override bool Equals (object other)
 146                 {
 147                         if (!(other is Nullable<T>))
 148                                 return false;
 149
 150                         return Equals ((Nullable <T>) other);
 151                 }
 152
 153                 public bool Equals (Nullable<T> other)
 154                 {
 155                         if (other.has_value != has_value)
 156                                 return false;
 157
 158                         if (has_value == false)
 159                                 return true;
 160
 161                         return other.value.Equals (value);
 162                 }
 163
 164                 [Obsolete]
 165                 public static Nullable<T> FromObject (object value)
 166                 {
 167                         return Nullable.FromObject<T> (value);
 168                 }
 169
 170                 public override int GetHashCode ()
 171                 {
 172                         if (!has_value)
 173                                 return 0;
 174
 175                         return value.GetHashCode ();
 176                 }
 177
 178                 [Obsolete]
 179                 public T GetValueOrDefault ()
 180                 {
 181                         return Nullable.GetValueOrDefault<T> (this, default (T));
 182                 }
 183
 184                 [Obsolete]
 185                 public T GetValueOrDefault (T def_value)
 186                 {
 187                         return Nullable.GetValueOrDefault<T> (this, def_value);
 188                 }
 189
 190                 public object ToObject ()
 191                 {
 192                         if (!has_value)
 193                                 return null;
 194
 195                         return (object)value;
 196                 }
 197
 198                 public override string ToString ()
 199                 {
 200                         if (has_value)
 201                                 return value.ToString ();
 202                         else
 203                                 return "";
 204                 }
 205
 206                 public static implicit operator Nullable<T> (T value)
 207                 {
 208                         return new Nullable<T> (value);
 209                 }
 210
 211                 public static explicit operator T (Nullable<T> value)
 212                 {
 213                         return value.Value;
 214                 }
 215
 216                 public static bool operator == (Nullable<T> left, Nullable<T> right)
 217                 {
 218                         return left.Equals (right);
 219                 }
 220
 221                 public static bool operator != (Nullable<T> left, Nullable<T> right)
 222                 {
 223                         return !left.Equals (right);
 224                 }
 225         }
 226 }
 227 #endif