Interface IObserver<TValue, TResult>

Provides a mechanism for receiving push-based notifications and returning a response.

Namespace: System.Reactive
Assembly: System.Reactive.Interfaces.dll
Syntax
public interface IObserver<in TValue, out TResult>
Type Parameters
Name Description
TValue

The type of the elements received by the observer. This type parameter is contravariant. That is, you can use either the type you specified or any type that is less derived. For more information about covariance and contravariance, see Covariance and Contravariance in Generics.
TResult

The type of the result returned from the observer's notification handlers. This type parameter is covariant. That is, you can use either the type you specified or any type that is more derived. For more information about covariance and contravariance, see Covariance and Contravariance in Generics.

Methods

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OnCompleted()

Notifies the observer of the end of the sequence.

Declaration
TResult OnCompleted()
Returns
Type Description
TResult

Result returned upon observation of the sequence completion.
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OnError(Exception)

Notifies the observer that an exception has occurred.

Declaration
TResult OnError(Exception exception)
Parameters
Type Name Description
Exception exception

The exception that occurred.
Returns
Type Description
TResult

Result returned upon observation of an error.
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OnNext(TValue)

Notifies the observer of a new element in the sequence.

Declaration
TResult OnNext(TValue value)
Parameters
Type Name Description
TValue value

The new element in the sequence.
Returns
Type Description
TResult

Result returned upon observation of a new element.