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72 lines
2.4 KiB
72 lines
2.4 KiB
# Cancellation Token Provider
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A `CancellationToken` enables cooperative cancellation between threads, thread pool work items, or `Task` objects. To handle the possible cancellation of the operation, ABP Framework provides `ICancellationTokenProvider` to obtain the `CancellationToken` itself from the source.
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> To get more information about `CancellationToken`, see [Microsoft Documentation](https://docs.microsoft.com/en-us/dotnet/api/system.threading.cancellationtoken).
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## ICancellationTokenProvider
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`ICancellationTokenProvider` is an abstraction to provide `CancellationToken` for different scenarios.
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Generally, you should pass the `CancellationToken` as a parameter for your method to use it. With the `ICancellationTokenProvider` you don't need to pass `CancellationToken` for every method. `ICancellationTokenProvider` can be injected with the **dependency injection** and provides the token from it's source.
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**Example:**
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```csharp
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using System.Threading.Tasks;
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using Volo.Abp.DependencyInjection;
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using Volo.Abp.Threading;
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namespace MyProject
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{
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public class MyService : ITransientDependency
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{
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private readonly ICancellationTokenProvider _cancellationTokenProvider;
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public MyService(ICancellationTokenProvider cancellationTokenProvider)
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{
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_cancellationTokenProvider = cancellationTokenProvider;
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}
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public async Task DoItAsync()
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{
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while (_cancellationTokenProvider.Token.IsCancellationRequested == false)
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{
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// ...
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}
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}
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}
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}
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```
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## Built-in providers
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- `NullCancellationTokenProvider`
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The `NullCancellationTokenProvider` is a built in provider and it supply always `CancellationToken.None`.
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- `HttpContextCancellationTokenProvider`
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The `HttpContextCancellationTokenProvider` is a built in default provider for ABP Web applications. It simply provides a `CancellationToken` that is source of the web request from the `HttpContext`.
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## Implementing the ICancellationTokenProvider
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You can easily create your CancellationTokenProvider by creating a class that implements the `ICancellationTokenProvider` interface, as shown below:
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```csharp
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using System.Threading;
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namespace AbpDemo
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{
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public class MyCancellationTokenProvider : ICancellationTokenProvider
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{
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public CancellationToken Token { get; }
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private MyCancellationTokenProvider()
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{
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}
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}
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}
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```
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