4 // Martin Baulig (martin@ximian.com)
5 // Marek Safar (marek.safar@gmail.com)
7 // (C) 2004 Novell, Inc.
11 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
13 // Permission is hereby granted, free of charge, to any person obtaining
14 // a copy of this software and associated documentation files (the
15 // "Software"), to deal in the Software without restriction, including
16 // without limitation the rights to use, copy, modify, merge, publish,
17 // distribute, sublicense, and/or sell copies of the Software, and to
18 // permit persons to whom the Software is furnished to do so, subject to
19 // the following conditions:
21 // The above copyright notice and this permission notice shall be
22 // included in all copies or substantial portions of the Software.
24 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
25 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
26 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
27 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
28 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
29 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
30 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
33 using System.Reflection;
34 using System.Collections.Generic;
35 using System.Runtime.CompilerServices;
36 using System.Runtime.InteropServices;
41 public static class Nullable {
46 public static int Compare<T> (T? n1, T? n2) where T: struct
52 return Comparer<T>.Default.Compare (n1.value, n2.value);
55 return n2.has_value ? -1 : 0;
61 public static bool Equals<T> (T? n1, T? n2) where T: struct
63 if (n1.has_value != n2.has_value)
69 return EqualityComparer<T>.Default.Equals (n1.value, n2.value);
72 public static Type GetUnderlyingType (Type nullableType)
74 if (nullableType == null)
75 throw new ArgumentNullException ("nullableType");
76 if (nullableType.IsGenericType && nullableType.GetGenericTypeDefinition () == typeof (Nullable<>))
77 return nullableType.GetGenericArguments ()[0];
84 public struct Nullable<T> where T: struct
86 #region Sync with runtime code
88 internal bool has_value;
91 public Nullable (T value)
93 this.has_value = true;
97 public bool HasValue {
98 get { return has_value; }
104 throw new InvalidOperationException ("Nullable object must have a value.");
110 public override bool Equals (object other)
113 return has_value == false;
114 if (!(other is Nullable<T>))
117 return Equals ((Nullable <T>) other);
120 bool Equals (Nullable<T> other)
122 if (other.has_value != has_value)
125 if (has_value == false)
128 return other.value.Equals (value);
131 public override int GetHashCode ()
136 return value.GetHashCode ();
139 public T GetValueOrDefault ()
141 return has_value ? value : default (T);
144 public T GetValueOrDefault (T defaultValue)
146 return has_value ? value : defaultValue;
149 public override string ToString ()
152 return value.ToString ();
157 public static implicit operator Nullable<T> (T value)
159 return new Nullable<T> (value);
162 public static explicit operator T (Nullable<T> value)
168 // These are called by the JIT
170 #pragma warning disable 169
172 // JIT implementation of box valuetype System.Nullable`1<T>
174 static object Box (T? o)
182 static T? Unbox (object o)
188 #pragma warning restore 169