Class Optional

Various extension and factory methods for constructing optional value.

Inheritance

Object

Optional

Inherited Members

Object.Equals(Object)

Object.Equals(Object, Object)

Object.GetHashCode()

Object.GetType()

Object.MemberwiseClone()

Object.ReferenceEquals(Object, Object)

Object.ToString()

Namespace: DotNext

Assembly: DotNext.dll

Syntax

public static class Optional

Methods

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

Returns the second value if the first is empty.

Declaration

public static Optional<T> Coalesce<T>(this in Optional<T> first, in Optional<T> second)

Parameters

Type	Name	Description
Optional<T>	first	The first optional value.
Optional<T>	second	The second optional value.

Returns

Type	Description
Optional<T>	The second value if the first is empty; otherwise, the first value.

Type Parameters

Name	Description
T	Type of value.

Convert<TInput, TOutput>(Task<Optional<TInput>>, Converter<TInput, TOutput>)

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 static Task<Optional<TOutput>> Convert<TInput, TOutput>(this Task<Optional<TInput>> task, Converter<TInput, TOutput> converter)

Parameters

Type	Name	Description
Task<Optional<TInput>>	task	The task containing Optional value.
Converter<TInput, TOutput>	converter	A mapping function to be applied to the value, if present.

Returns

Type	Description
Task<Optional<TOutput>>	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
TInput	The type of stored in the Optional container.
TOutput	The type of the result of the mapping function.

GetUnderlyingType(Type)

Returns the underlying type argument of the specified optional type.

Declaration

public static Type GetUnderlyingType(Type optionalType)

Parameters

Type	Name	Description
Type	optionalType	Optional type.

Returns

Type	Description
Type	Underlying type argument of optional type; otherwise, null.

If<T>(Task<Optional<T>>, 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 static Task<Optional<T>> If<T>(this Task<Optional<T>> task, Predicate<T> condition)

Parameters

Type	Name	Description
Task<Optional<T>>	task	The task returning optional value.
Predicate<T>	condition	A predicate to apply to the value, if present.

Returns

Type	Description
Task<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.

Type Parameters

Name	Description
T	Type of the value.

IsOptional(Type)

Indicates that specified type is optional type.

Declaration

public static bool IsOptional(this Type optionalType)

Parameters

Type	Name	Description
Type	optionalType	The type to check.

Returns

Type	Description
Boolean	true, if specified type is optional type; otherwise, false.

None<T>()

Returns empty value.

Declaration

public static Optional<T> None<T>()

Returns

Type	Description
Optional<T>	The empty value.

Type Parameters

Name	Description
T	The type of empty result.

Null<T>()

Wraps null value to Optional<T> container.

Declaration

public static Optional<T> Null<T>()

    where T : class

Returns

Type	Description
Optional<T>	The Optional<T> instance representing null value.

Type Parameters

Name	Description
T	The reference type.

Or<T>(Task<Optional<T>>, T)

Returns the value if present; otherwise return default value.

Declaration

public static Task<T> Or<T>(this Task<Optional<T>> task, T defaultValue)

Parameters

Type	Name	Description
Task<Optional<T>>	task	The task returning optional value.
T	defaultValue	The value to be returned if there is no value present.

Returns

Type	Description
Task<T>	The value, if present, otherwise default.

Type Parameters

Name	Description
T	The type of the value.

OrDefault<T>(Task<Optional<T>>)

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

Declaration

public static Task<T> OrDefault<T>(this Task<Optional<T>> task)

Parameters

Type	Name	Description
Task<Optional<T>>	task	The task returning optional value.

Returns

Type	Description
Task<T>	The value, if present, otherwise default.

Type Parameters

Name	Description
T	Type of the value.

OrInvoke<T>(Task<Optional<T>>, Func<T>)

Returns the value if present; otherwise invoke delegate.

Declaration

public static Task<T> OrInvoke<T>(this Task<Optional<T>> task, Func<T> defaultFunc)

Parameters

Type	Name	Description
Task<Optional<T>>	task	The task returning optional value.
Func<T>	defaultFunc	A delegate to be invoked if value is not present.

Returns

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

Type Parameters

Name	Description
T	Type of the value.

OrNull<T>(Optional<T>)

If a value is present, returns the value, otherwise null.

Declaration

public static T? OrNull<T>(this in Optional<T> value)

    where T : struct

Parameters

Type	Name	Description
Optional<T>	value	Optional value.

Returns

Type	Description
Nullable<T>	Nullable value.

Type Parameters

Name	Description
T	Value type.

OrNull<T>(Task<Optional<T>>)

If a value is present, returns the value, otherwise null.

Declaration

public static Task<T?> OrNull<T>(this Task<Optional<T>> task)

    where T : struct

Parameters

Type	Name	Description
Task<Optional<T>>	task	The task returning optional value.

Returns

Type	Description
Task<Nullable<T>>	Nullable value.

Type Parameters

Name	Description
T	The type of the value.

OrThrow<T, TException>(Task<Optional<T>>)

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

Declaration

public static Task<T> OrThrow<T, TException>(this Task<Optional<T>> task)

    where TException : Exception, new()

Parameters

Type	Name	Description
Task<Optional<T>>	task	The task returning optional value.

Returns

Type	Description
Task<T>	The value, if present.

Type Parameters

Name	Description
T	Type of the value.
TException	Type of exception to throw.

OrThrow<T, TException>(Task<Optional<T>>, Func<TException>)

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

Declaration

public static Task<T> OrThrow<T, TException>(this Task<Optional<T>> task, Func<TException> exceptionFactory)

    where TException : Exception

Parameters

Type	Name	Description
Task<Optional<T>>	task	The task returning optional value.
Func<TException>	exceptionFactory	Exception factory.

Returns

Type	Description
Task<T>	The value, if present.

Type Parameters

Name	Description
T	Type of the value.
TException	Type of exception to throw.

Some<T>(T)

Wraps the value to Optional<T> container.

Declaration

public static Optional<T> Some<T>(T value)

Parameters

Type	Name	Description
T	value	The value to be wrapped.

Returns

Type	Description
Optional<T>	The optional container.

Type Parameters

Name	Description
T	The type of the value.

ToOptional<T>(Nullable<T>)

Constructs optional value from nullable reference type.

Declaration

public static Optional<T> ToOptional<T>(this in T? value)

    where T : struct

Parameters

Type	Name	Description
Nullable<T>	value	The value to convert.

Returns

Type	Description
Optional<T>	The value wrapped into Optional container.

Type Parameters

Name	Description
T	Type of value.