Struct Optional<T>

A container object which may or may not contain a value.

Implements

IEquatable<Optional<T>>

IEquatable<T>

IStructuralEquatable

ISerializable

Inherited Members

Object.Equals(Object, Object)

Object.GetType()

Object.ReferenceEquals(Object, Object)

Namespace: DotNext

Assembly: DotNext.dll

Syntax

[Serializable]
public struct Optional<T> : IEquatable<Optional<T>>, IEquatable<T>, IStructuralEquatable, ISerializable

Type Parameters

Name	Description
T	Type of value.

Constructors

Optional(T)

Constructs non-empty container.

Declaration

public Optional(T value)

Parameters

Type	Name	Description
T	value	A value to be placed into container.

Remarks

The property langword_csharp_IsNull of the constructed object may be true if value is null. The property langword_csharp_IsUndefined of the constructed object is always false.

Properties

Empty

Represents optional container without value.

Declaration

[Obsolete("Use None static property instead")]
public static Optional<T> Empty { get; }

Property Value

Type	Description
Optional<T>

Remarks

The property IsUndefined of returned object is always true.

HasValue

Indicates whether the value is present.

Declaration

public bool HasValue { get; }

Property Value

Type	Description
Boolean

Remarks

If this property is true then IsUndefined and IsNull equal to false.

IsNull

Indicates that the value is null.

Declaration

public bool IsNull { get; }

Property Value

Type	Description
Boolean

Remarks

This property returns true only if this instance was constructed using Optional(T) with null argument.

IsUndefined

Indicates that the value is undefined.

Declaration

public bool IsUndefined { get; }

Property Value

Type	Description
Boolean

See Also

None

None

Represents optional container without value.

Declaration

public static Optional<T> None { get; }

Property Value

Type	Description
Optional<T>

Remarks

The property IsUndefined of returned object is always true.

Value

If a value is present, returns the value, otherwise throw exception.

Declaration

public T Value { get; }

Property Value

Type	Description
T

Exceptions

Type	Condition
InvalidOperationException	No value is present.

Methods

Box()

Boxes value encapsulated by this object.

Declaration

public Optional<object> Box()

Returns

Type	Description
Optional<Object>	The boxed value.

Convert<TResult>(ValueFunc<T, TResult>)

If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result. Otherwise returns None.

Declaration

public Optional<TResult> Convert<TResult>(in ValueFunc<T, TResult> mapper)

Parameters

Type	Name	Description
ValueFunc<T, TResult>	mapper	A mapping function to be applied to the value, if present.

Returns

Type	Description
Optional<TResult>	An Optional describing the result of applying a mapping function to the value of this Optional, if a value is present, otherwise None.

Type Parameters

Name	Description
TResult	The type of the result of the mapping function.

Convert<TResult>(ValueFunc<T, Optional<TResult>>)

If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result. Otherwise returns None.

Declaration

public Optional<TResult> Convert<TResult>(in ValueFunc<T, Optional<TResult>> mapper)

Parameters

Type	Name	Description
ValueFunc<T, Optional<TResult>>	mapper	A mapping function to be applied to the value, if present.

Returns

Type	Description
Optional<TResult>	An Optional describing the result of applying a mapping function to the value of this Optional, if a value is present, otherwise None.

Type Parameters

Name	Description
TResult	The type of the result of the mapping function.

Convert<TResult>(Converter<T, TResult>)

If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result. Otherwise returns None.

Declaration

public Optional<TResult> Convert<TResult>(Converter<T, TResult> mapper)

Parameters

Type	Name	Description
Converter<T, TResult>	mapper	A mapping function to be applied to the value, if present.

Returns

Type	Description
Optional<TResult>	An Optional describing the result of applying a mapping function to the value of this Optional, if a value is present, otherwise None.

Type Parameters

Name	Description
TResult	The type of the result of the mapping function.

Convert<TResult>(Converter<T, Optional<TResult>>)

If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result. Otherwise returns None.

Declaration

public Optional<TResult> Convert<TResult>(Converter<T, Optional<TResult>> mapper)

Parameters

Type	Name	Description
Converter<T, Optional<TResult>>	mapper	A mapping function to be applied to the value, if present.

Returns

Type	Description
Optional<TResult>	An Optional describing the result of applying a mapping function to the value of this Optional, if a value is present, otherwise None.

Type Parameters

Name	Description
TResult	The type of the result of the mapping function.

Equals(T)

Determines whether this container stored the same value as the specified value.

Declaration

public bool Equals(T other)

Parameters

Type	Name	Description
T	other	Other value to compare.

Returns

Type	Description
Boolean	true if Value is equal to other; otherwise, false.

Equals(Optional<T>)

Determines whether this container stores the same value as other.

Declaration

public bool Equals(Optional<T> other)

Parameters

Type	Name	Description
Optional<T>	other	Other container to compare.

Returns

Type	Description
Boolean	true if this container stores the same value as other; otherwise, false.

Equals(Object)

Determines whether this container stores the same value as other.

Declaration

public override bool Equals(object other)

Parameters

Type	Name	Description
Object	other	Other container to compare.

Returns

Type	Description
Boolean	true if this container stores the same value as other; otherwise, false.

Overrides

ValueType.Equals(Object)

Equals(Object, IEqualityComparer)

Performs equality check between stored value and the specified value using method Equals(Object, Object).

Declaration

public bool Equals(object other, IEqualityComparer comparer)

Parameters

Type	Name	Description
Object	other	Other object to compare with Value.
IEqualityComparer	comparer	The comparer implementing custom equality check.

Returns

Type	Description
Boolean	true if other is equal to Value using custom check; otherwise, false.

GetHashCode()

Computes hash code of the stored value.

Declaration

public override int GetHashCode()

Returns

Type	Description
Int32	The hash code of the stored value.

Overrides

ValueType.GetHashCode()

Remarks

This method calls GetHashCode() for the object Value.

GetHashCode(IEqualityComparer)

Computes hash code for the stored value using method GetHashCode(Object).

Declaration

public int GetHashCode(IEqualityComparer comparer)

Parameters

Type	Name	Description
IEqualityComparer	comparer	The comparer implementing hash code function.

Returns

Type	Description
Int32	The hash code of Value.

If(ValueFunc<T, Boolean>)

If a value is present, and the value matches the given predicate, return an Optional describing the value, otherwise return an empty Optional.

Declaration

public Optional<T> If(in ValueFunc<T, bool> condition)

Parameters

Type	Name	Description
ValueFunc<T, Boolean>	condition	A predicate to apply to the value, if present.

Returns

Type	Description
Optional<T>	An Optional describing the value of this Optional if a value is present and the value matches the given predicate, otherwise an empty Optional.

If(Predicate<T>)

If a value is present, and the value matches the given predicate, return an Optional describing the value, otherwise return an empty Optional.

Declaration

public Optional<T> If(Predicate<T> condition)

Parameters

Type	Name	Description
Predicate<T>	condition	A predicate to apply to the value, if present.

Returns

Type	Description
Optional<T>	An Optional describing the value of this Optional if a value is present and the value matches the given predicate, otherwise an empty Optional.

Or(T)

Returns the value if present; otherwise return default value.

Declaration

public T Or(T defaultValue)

Parameters

Type	Name	Description
T	defaultValue	The value to be returned if there is no value present.

Returns

Type	Description
T	The value, if present, otherwise defaultValue.

OrDefault()

If a value is present, returns the value, otherwise return default value.

Declaration

public T OrDefault()

Returns

Type	Description
T	The value, if present, otherwise default.

OrInvoke(ValueFunc<T>)

Returns the value if present; otherwise invoke delegate.

Declaration

public T OrInvoke(in ValueFunc<T> defaultFunc)

Parameters

Type	Name	Description
ValueFunc<T>	defaultFunc	A delegate to be invoked if value is not present.

Returns

Type	Description
T	The value, if present, otherwise returned from delegate.

OrInvoke(Func<T>)

Returns the value if present; otherwise invoke delegate.

Declaration

public T OrInvoke(Func<T> defaultFunc)

Parameters

Type	Name	Description
Func<T>	defaultFunc	A delegate to be invoked if value is not present.

Returns

Type	Description
T	The value, if present, otherwise returned from delegate.

OrThrow<TException>()

If a value is present, returns the value, otherwise throw exception.

Declaration

public T OrThrow<TException>()

    where TException : Exception, new()

Returns

Type	Description
T	The value, if present.

Type Parameters

Name	Description
TException	Type of exception to throw.

OrThrow<TException>(ValueFunc<TException>)

If a value is present, returns the value, otherwise throw exception.

Declaration

public T OrThrow<TException>(in ValueFunc<TException> exceptionFactory)

    where TException : Exception

Parameters

Type	Name	Description
ValueFunc<TException>	exceptionFactory	Exception factory.

Returns

Type	Description
T	The value, if present.

Type Parameters

Name	Description
TException	Type of exception to throw.

OrThrow<TException>(Func<TException>)

If a value is present, returns the value, otherwise throw exception.

Declaration

public T OrThrow<TException>(Func<TException> exceptionFactory)

    where TException : Exception

Parameters

Type	Name	Description
Func<TException>	exceptionFactory	Exception factory.

Returns

Type	Description
T	The value, if present.

Type Parameters

Name	Description
TException	Type of exception to throw.

ToString()

Returns textual representation of this object.

Declaration

public override string ToString()

Returns

Type	Description
String	The textual representation of this object.

Overrides

ValueType.ToString()

TryGet(out T)

Attempts to extract value from container if it is present.

Declaration

public bool TryGet(out T value)

Parameters

Type	Name	Description
T	value	Extracted value.

Returns

Type	Description
Boolean	true if value is present; otherwise, false.

TryGet(out T, out Boolean)

Attempts to extract value from container if it is present.

Declaration

public bool TryGet(out T value, out bool isNull)

Parameters

Type	Name	Description
T	value	Extracted value.
Boolean	isNull	true if underlying value is null; otherwise, false.

Returns

Type	Description
Boolean	true if value is present; otherwise, false.

Operators

BitwiseOr(Optional<T>, Optional<T>)

Returns non-empty container.

Declaration

public static Optional<T> operator |(in Optional<T> first, in Optional<T> second)

Parameters

Type	Name	Description
Optional<T>	first	The first container.
Optional<T>	second	The second container.

Returns

Type	Description
Optional<T>	The first non-empty container.

See Also

Coalesce<T>(Optional<T>, Optional<T>)

Equality(Optional<T>, Optional<T>)

Determines whether two containers store the same value.

Declaration

public static bool operator ==(in Optional<T> first, in Optional<T> second)

Parameters

Type	Name	Description
Optional<T>	first	The first container to compare.
Optional<T>	second	The second container to compare.

Returns

Type	Description
Boolean	true, if both containers store the same value; otherwise, false.

ExclusiveOr(Optional<T>, Optional<T>)

Determines whether two containers are empty or have values.

Declaration

public static Optional<T> operator ^(in Optional<T> first, in Optional<T> second)

Parameters

Type	Name	Description
Optional<T>	first	The first container.
Optional<T>	second	The second container.

Returns

Type	Description
Optional<T>	true, if both containers are empty or have values; otherwise, false.

Explicit(Optional<T> to T)

Extracts value stored in the Optional container.

Declaration

public static explicit operator T(in Optional<T> optional)

Parameters

Type	Name	Description
Optional<T>	optional	The container.

Returns

Type	Description
T

Exceptions

Type	Condition
InvalidOperationException	No value is present.

False(Optional<T>)

Checks whether the container has no value.

Declaration

public static bool operator false (in Optional<T> optional)

Parameters

Type	Name	Description
Optional<T>	optional	The container to check.

Returns

Type	Description
Boolean	true if this container has no value; otherwise, false.

Implicit(T to Optional<T>)

Wraps value into Optional container.

Declaration

public static implicit operator Optional<T>(T value)

Parameters

Type	Name	Description
T	value	The value to convert.

Returns

Type	Description
Optional<T>

Inequality(Optional<T>, Optional<T>)

Determines whether two containers store the different values.

Declaration

public static bool operator !=(in Optional<T> first, in Optional<T> second)

Parameters

Type	Name	Description
Optional<T>	first	The first container to compare.
Optional<T>	second	The second container to compare.

Returns

Type	Description
Boolean	true, if both containers store the different values; otherwise, false.

True(Optional<T>)

Checks whether the container has value.

Declaration

public static bool operator true (in Optional<T> optional)

Parameters

Type	Name	Description
Optional<T>	optional	The container to check.

Returns

Type	Description
Boolean	true if this container has value; otherwise, false.

Explicit Interface Implementations

ISerializable.GetObjectData(SerializationInfo, StreamingContext)

Declaration

void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)

Parameters

Type	Name	Description
SerializationInfo	info
StreamingContext	context

Implements

System.IEquatable<T>

System.IEquatable<T>

System.Collections.IStructuralEquatable

System.Runtime.Serialization.ISerializable

Extension Methods

Optional.Coalesce<T>(Optional<T>, Optional<T>)

ValueTypeExtensions.IsOneOf<T>(T, IEnumerable<T>)

ValueTypeExtensions.IsOneOf<T>(T, T[])

Sequence.Skip<TEnumerator, T>(ref TEnumerator, Int32)

ExpressionBuilder.Const<T>(T)