)} ,System.Linq.Expressions.Expression})}
Qbservable.FirstOrDefaultAsync(IQbservable) method¶
Defined in
Type: Qbservable
Namespace: System.Reactive.Linq
Assembly: System.Reactive.dll
Applies to
netstandard2.0
Overloads¶
- 1.
public static IQbservable<TSource?> FirstOrDefaultAsync<TSource>(this IQbservable<TSource> source) - 2.
public static IQbservable<TSource?> FirstOrDefaultAsync<TSource>(this IQbservable<TSource> source, Expression<Func<TSource, bool>> predicate)
1. Overload¶
public static IQbservable<TSource?> FirstOrDefaultAsync<TSource>(this IQbservable<TSource> source)
Summary: Returns the first element of an observable sequence, or a default value if no such element exists.
Type parameters
| Name | Description |
|---|---|
TSource | The type of the elements in the source sequence. |
Parameters
| Name | Type | Description |
|---|---|---|
source | [IQbservable | Source observable sequence. |
Returns: IQbservable
Exceptions
| Type | Condition |
|---|---|
| System.ArgumentNullException | source is null. |
2. Overload¶
public static IQbservable<TSource?> FirstOrDefaultAsync<TSource>(this IQbservable<TSource> source, Expression<Func<TSource, bool>> predicate)
Summary: Returns the first element of an observable sequence that satisfies the condition in the predicate, or a default value if no such element exists.
Type parameters
| Name | Description |
|---|---|
TSource | The type of the elements in the source sequence. |
Parameters
| Name | Type | Description |
|---|---|---|
source | [IQbservable | Source observable sequence. |
predicate | Expression | A predicate function to evaluate for elements in the source sequence. |
Returns: IQbservable
Exceptions
| Type | Condition |
|---|---|
| System.ArgumentNullException | source or predicate is null. |