www.pudn.com > sudoku.rar > NullableInt.cs

//-------------------------------------------------------------------------- 
//  
//  Copyright (c) Microsoft Corporation.  All rights reserved.  
//  
//  File: NullableInt.cs 
// 
//  Description: .NET 1.x substitute for Nullable in 2.0 
//  
//-------------------------------------------------------------------------- 
 
using System; 
using System.Text; 
 
namespace Microsoft.Sudoku.Nullables 
{ 
	/// 
A nullable int.
 
	[Serializable] 
	public struct NullableInt 
	{ 
		/// 
The contained value.
 
		private int _value; 
		/// 
Whether this nullable has a value.
 
		private bool _hasValue; 
 
		/// 
Initializes the nullable.
 
		/// The value with which to initialize this nullable. 
		public NullableInt(int value) 
		{ 
			_value = value; 
			_hasValue = true; 
		} 
 
		/// 
Gets the value of the nullable.
 
		public int Value 
		{ 
			get 
			{ 
				if (!_hasValue) throw new InvalidOperationException(); 
				return _value; 
			} 
		} 
 
		/// 
Gets whether this nullable has a value.
 
		public bool HasValue { get { return _hasValue; } } 
 
		/// 
Implicit cast from a NullableInt to a int.
 
		/// The value to be cast. 
		/// The cast int. 
		public static implicit operator int(NullableInt value) 
		{ 
			return value.Value; 
		} 
 
		/// 
Implicit cast from a int to a NullableInt.
 
		/// The value to be cast. 
		/// The cast NullableInt. 
		public static implicit operator NullableInt(int value) 
		{ 
			return new NullableInt(value); 
		} 
 
		/// 
Implicit cast from a null value to a NullableInt.
 
		/// Must be null. 
		/// A null NullableInt. 
		public static implicit operator NullableInt(NullObject value) 
		{ 
			if (value != null) throw new ArgumentOutOfRangeException("value"); 
			return new NullableInt(); 
		} 
 
		/// 
Equality check for two NullableInts.
 
		/// The first value. 
		/// The second value. 
		/// true if the values are equal; otherwise, false. 
		public static bool operator ==(NullableInt value1, NullableInt value2) 
		{ 
			return (!value1.HasValue && !value2.HasValue) || (value1.HasValue && value2.HasValue && value1._value == value2._value); 
		} 
 
		/// 
Inequality check for two NullableInts.
 
		/// The first value. 
		/// The second value. 
		/// true if the values are equal; otherwise, false. 
		public static bool operator !=(NullableInt value1, NullableInt value2) 
		{ 
			return !(value1 == value2); 
		} 
 
		/// 
Equality check for a nullable and an int.
 
		/// The first value. 
		/// The second value. 
		/// true if the values are equal; otherwise, false. 
		public static bool operator ==(NullableInt value1, int value2) 
		{ 
			return value1.HasValue && value1.Value == value2; 
		} 
 
		/// 
Inequality check for a nullable and an int.
 
		/// The first value. 
		/// The second value. 
		/// true if the values are equal; otherwise, false. 
		public static bool operator !=(NullableInt value1, int value2) 
		{ 
			return !(value1 == value2); 
		} 
 
		/// 
Equality check for a NullableInt and a null value.
 
		/// The first value. 
		/// The null value. 
		/// true if the values are equal; otherwise, false. 
		public static bool operator ==(NullableInt value1, NullObject value2) 
		{ 
			return !value1.HasValue && value2 == null; 
		} 
 
		/// 
Inequality check for a NullableInt and a null value.
 
		/// The first value. 
		/// The null value. 
		/// true if the values are equal; otherwise, false. 
		public static bool operator !=(NullableInt value1, NullObject value2) 
		{ 
			return !(value1 == value2); 
		} 
 
		/// 
 
		/// 	Determines whether the specified  is equal to the current . 
		/// 
 
		/// The  to compare with the current . 
		///  
		/// 	 
		/// 		 if the specified  is equal to the 
		///    current ; otherwise, . 
		///  
		public override bool Equals(object obj) 
		{ 
			if (obj is NullableInt) return base.Equals(obj); 
			else if (obj is int) return HasValue && Value == (int)obj; 
			else if (obj == null) return !HasValue; 
			else return false; 
		} 
 
		/// 
 
		/// 	Serves as a hash function for a particular type, suitable 
		///       for use in hashing algorithms and data structures like a hash table. 
		/// 
 
		///  
		/// 	A hash code for the current . 
		///  
		public override int GetHashCode() { return base.GetHashCode(); } 
	} 
}