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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System.Collections.Generic;
using System.Runtime.Versioning;
namespace System
{
// Because we have special type system support that says a boxed Nullable<T>
// can be used where a boxed<T> is use, Nullable<T> can not implement any intefaces
// at all (since T may not). Do NOT add any interfaces to Nullable!
//
[Serializable]
[NonVersionable] // This only applies to field layout
[System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
public partial struct Nullable<T> where T : struct
{
private readonly bool hasValue; // Do not rename (binary serialization)
internal T value; // Do not rename (binary serialization) or make readonly (can be mutated in ToString, etc.)
[NonVersionable]
public Nullable(T value)
{
this.value = value;
hasValue = true;
}
public bool HasValue
{
[NonVersionable]
get
{
return hasValue;
}
}
public T Value
{
get
{
if (!hasValue)
{
ThrowHelper.ThrowInvalidOperationException_InvalidOperation_NoValue();
}
return value;
}
}
[NonVersionable]
public T GetValueOrDefault()
{
return value;
}
[NonVersionable]
public T GetValueOrDefault(T defaultValue)
{
return hasValue ? value : defaultValue;
}
public override bool Equals(object? other)
{
if (!hasValue) return other == null;
if (other == null) return false;
return value.Equals(other);
}
public override int GetHashCode()
{
return hasValue ? value.GetHashCode() : 0;
}
public override string? ToString()
{
return hasValue ? value.ToString() : "";
}
[NonVersionable]
public static implicit operator Nullable<T>(T value)
{
return new Nullable<T>(value);
}
[NonVersionable]
public static explicit operator T(Nullable<T> value)
{
return value!.Value;
}
}
public static class Nullable
{
public static int Compare<T>(Nullable<T> n1, Nullable<T> n2) where T : struct
{
if (n1.HasValue)
{
if (n2.HasValue) return Comparer<T>.Default.Compare(n1.value, n2.value);
return 1;
}
if (n2.HasValue) return -1;
return 0;
}
public static bool Equals<T>(Nullable<T> n1, Nullable<T> n2) where T : struct
{
if (n1.HasValue)
{
if (n2.HasValue) return EqualityComparer<T>.Default.Equals(n1.value, n2.value);
return false;
}
if (n2.HasValue) return false;
return true;
}
// If the type provided is not a Nullable Type, return null.
// Otherwise, returns the underlying type of the Nullable type
public static Type? GetUnderlyingType(Type nullableType)
{
if ((object)nullableType == null)
{
throw new ArgumentNullException(nameof(nullableType));
}
#if CORERT
// This is necessary to handle types without reflection metadata
if (nullableType.TryGetEEType(out EETypePtr nullableEEType))
{
if (nullableEEType.IsGeneric)
{
if (nullableEEType.IsNullable)
{
return Internal.Reflection.Core.NonPortable.RuntimeTypeUnifier.GetRuntimeTypeForEEType(nullableEEType.NullableType);
}
}
return null;
}
#endif
if (nullableType.IsGenericType && !nullableType.IsGenericTypeDefinition)
{
// instantiated generic type only
Type genericType = nullableType.GetGenericTypeDefinition();
if (object.ReferenceEquals(genericType, typeof(Nullable<>)))
{
return nullableType.GetGenericArguments()[0];
}
}
return null;
}
}
}
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