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ObservableAsync.FirstOrDefaultAsync(IObservableAsync, Func, T?) method¶

Defined in

Type: ObservableAsync Namespace: ReactiveUI.Extensions.Async Assembly: ReactiveUI.Extensions.dll

Applies to

net10.0, net10.0-browserwasm1.0, net10.0-desktop1.0, net9.0, net9.0-browserwasm1.0, net9.0-desktop1.0, net8.0, net8.0-ios17.5, net8.0-maccatalyst17.5, net8.0-macos14.2, net8.0-macos14.5, net8.0-tvos17.2, netstandard2.1, net462, net481

Overloads¶

1. public static ValueTask<T?> FirstOrDefaultAsync<T>(this IObservableAsync<T> @this, Func<T, bool> predicate, T? defaultValue)
2. public static ValueTask<T?> FirstOrDefaultAsync<T>(this IObservableAsync<T> @this, Func<T, bool> predicate, T? defaultValue, CancellationToken cancellationToken)
3. public static ValueTask<T?> FirstOrDefaultAsync<T>(this IObservableAsync<T> @this)
4. public static ValueTask<T?> FirstOrDefaultAsync<T>(this IObservableAsync<T> @this, CancellationToken cancellationToken)
5. public static ValueTask<T?> FirstOrDefaultAsync<T>(this IObservableAsync<T> @this, T? defaultValue)
6. public static ValueTask<T?> FirstOrDefaultAsync<T>(this IObservableAsync<T> @this, T? defaultValue, CancellationToken cancellationToken)

1. Overload¶

public static ValueTask<T?> FirstOrDefaultAsync<T>(this IObservableAsync<T> @this, Func<T, bool> predicate, T? defaultValue)

View source

Summary: Asynchronously returns the first element that matches the specified predicate, or a default value if no such element is found.

Type parameters

Name	Description
`T`	The type of elements in the source sequence.

Parameters

Name	Type	Description
`this`	[IObservableAsync](#	The source observable sequence.
`predicate`	Func	A function to test each element for a condition. The method returns the first element for which this predicate returns `true`.
`defaultValue`	`T?`	The value to return if no element satisfies the predicate.

Returns: ValueTask -- A value task that represents the asynchronous operation. The result contains the first element that matches the predicate, or defaultValue if no such element is found.

2. Overload¶

public static ValueTask<T?> FirstOrDefaultAsync<T>(this IObservableAsync<T> @this, Func<T, bool> predicate, T? defaultValue, CancellationToken cancellationToken)

Summary: Asynchronously returns the first element that matches the specified predicate, or a default value if no such element is found.

Type parameters

Name	Description
`T`	The type of elements in the source sequence.

Parameters

Name	Type	Description
`this`	[IObservableAsync](#	The source observable sequence.
`predicate`	Func	A function to test each element for a condition. The method returns the first element for which this predicate returns `true`.
`defaultValue`	`T?`	The value to return if no element satisfies the predicate.
`cancellationToken`	CancellationToken	A cancellation token that can be used to cancel the asynchronous operation.

Returns: ValueTask -- A value task that represents the asynchronous operation. The result contains the first element that matches the predicate, or defaultValue if no such element is found.

3. Overload¶

public static ValueTask<T?> FirstOrDefaultAsync<T>(this IObservableAsync<T> @this)

View source

Summary: Asynchronously returns the first element of the sequence, or a default value if the sequence contains no elements.

Type parameters

Name	Description
`T`	The type of elements in the source sequence.

Parameters

Name	Type	Description
`this`	[IObservableAsync](#	The source observable sequence.

Returns: ValueTask -- A value task that represents the asynchronous operation. The task result contains the first element of the sequence, or the default value for type T if the sequence is empty.

4. Overload¶

public static ValueTask<T?> FirstOrDefaultAsync<T>(this IObservableAsync<T> @this, CancellationToken cancellationToken)

View source

Summary: Asynchronously returns the first element of the sequence, or a default value if the sequence contains no elements.

Type parameters

Name	Description
`T`	The type of elements in the source sequence.

Parameters

Name	Type	Description
`this`	[IObservableAsync](#	The source observable sequence.
`cancellationToken`	CancellationToken	A cancellation token that can be used to cancel the asynchronous operation.

Returns: ValueTask -- A value task that represents the asynchronous operation. The task result contains the first element of the sequence, or the default value for type T if the sequence is empty.

5. Overload¶

public static ValueTask<T?> FirstOrDefaultAsync<T>(this IObservableAsync<T> @this, T? defaultValue)

View source

Summary: Asynchronously returns the first element of the sequence, or a specified default value if the sequence contains no elements.

Type parameters

Name	Description
`T`	The type of elements in the source sequence.

Parameters

Name	Type	Description
`this`	[IObservableAsync](#	The source observable sequence.
`defaultValue`	`T?`	The value to return if the sequence is empty.

Returns: ValueTask -- A task that represents the asynchronous operation. The task result contains the first element of the sequence, or defaultValue if the sequence is empty.

6. Overload¶

public static ValueTask<T?> FirstOrDefaultAsync<T>(this IObservableAsync<T> @this, T? defaultValue, CancellationToken cancellationToken)

Summary: Asynchronously returns the first element of the sequence, or a specified default value if the sequence contains no elements.

Type parameters

Name	Description
`T`	The type of elements in the source sequence.

Parameters

Name	Type	Description
`this`	[IObservableAsync](#	The source observable sequence.
`defaultValue`	`T?`	The value to return if the sequence is empty.
`cancellationToken`	CancellationToken	A cancellation token that can be used to cancel the asynchronous operation.

Returns: ValueTask -- A task that represents the asynchronous operation. The task result contains the first element of the sequence, or defaultValue if the sequence is empty.