Default parameter for CancellationToken in C#

Default parameter for CancellationToken in C#

It is possible to set a default parameter for CancellationToken in C#.

Here's an example:

 public async Task MyMethodAsync(CancellationToken cancellationToken = default(CancellationToken)) { // Do some async work await Task.Delay(1000, cancellationToken); }

In this example, the CancellationToken parameter has a default value of default(CancellationToken). This means that if the caller does not provide a CancellationToken, the default token will be used instead.

Note that it's important to use the default keyword here instead of null. null is not a valid value for CancellationToken, and passing null as the default value would result in a compile-time error.

Also, keep in mind that it's generally a good practice to always include a CancellationToken parameter in async methods, even if it has a default value. This allows callers to cancel the operation if necessary, which can be especially important in long-running or resource-intensive tasks.

Examples

1. "C# default parameter for CancellationToken with None"

Code:

// C# default parameter for CancellationToken with None public async Task SomeMethodAsync(CancellationToken cancellationToken = default) { // Your asynchronous code await Task.Delay(1000, cancellationToken); }

Description: This code defines a method with an asynchronous operation and a default parameter for CancellationToken with default, meaning no cancellation token by default.

2. "Default CancellationToken.None in C# method"

Code:

// Default CancellationToken.None in C# method public void SomeMethod(CancellationToken cancellationToken = default) { // Your synchronous code }

Description: This code defines a synchronous method with a default parameter for CancellationToken initialized to CancellationToken.None.

3. "C# default CancellationToken for Task.Run"

Code:

// C# default CancellationToken for Task.Run public async Task SomeMethodAsync() { CancellationToken cancellationToken = default; await Task.Run(() => { // Your parallel code }, cancellationToken); }

Description: This code demonstrates using Task.Run with a default CancellationToken in an asynchronous method.

4. "CancellationToken default parameter in C# constructor"

Code:

// CancellationToken default parameter in C# constructor public class MyClass { private readonly CancellationToken _cancellationToken; public MyClass(CancellationToken cancellationToken = default) { _cancellationToken = cancellationToken; } public void SomeMethod() { // Your code using _cancellationToken } }

Description: This code shows using a default parameter for CancellationToken in a class constructor.

5. "C# method with default CancellationToken for HttpClient"

Code:

// C# method with default CancellationToken for HttpClient public async Task<string> DownloadDataAsync(string url, CancellationToken cancellationToken = default) { using (var client = new HttpClient()) { return await client.GetStringAsync(url, cancellationToken); } }

Description: This code defines an asynchronous method that uses HttpClient with a default CancellationToken.

6. "C# default CancellationToken for Task.Delay"

Code:

// C# default CancellationToken for Task.Delay public async Task DelayAsync(int millisecondsDelay, CancellationToken cancellationToken = default) { await Task.Delay(millisecondsDelay, cancellationToken); }

Description: This code shows a method that utilizes Task.Delay with a default CancellationToken for asynchronous delay operations.

7. "C# default CancellationToken for Timer"

Code:

// C# default CancellationToken for Timer public void StartTimer(int intervalMilliseconds, CancellationToken cancellationToken = default) { var timer = new Timer(_ => { // Your timer callback code }, null, 0, intervalMilliseconds); }

Description: This code demonstrates starting a timer with a default CancellationToken for periodic tasks.

8. "Default CancellationToken.None for async method in C#"

Code:

// Default CancellationToken.None for async method in C# public async Task SomeMethodAsync(CancellationToken cancellationToken = default) { // Your asynchronous code await Task.Delay(1000, cancellationToken); }

Description: This code defines an asynchronous method with a default parameter for CancellationToken.None for cancellation handling.

9. "C# default CancellationToken for File I/O operation"

Code:

// C# default CancellationToken for File I/O operation public async Task<string> ReadFileAsync(string filePath, CancellationToken cancellationToken = default) { using (var streamReader = new StreamReader(filePath)) { return await streamReader.ReadToEndAsync(); } }

Description: This code illustrates using a default CancellationToken for asynchronous file I/O operations.

10. "C# method with default CancellationToken for database operation"

Code:

// C# method with default CancellationToken for database operation public async Task<IEnumerable<string>> QueryDatabaseAsync(string sqlQuery, CancellationToken cancellationToken = default) { // Your database query code using cancellationToken // Example: using Dapper or Entity Framework }

Description: This code demonstrates a method that performs an asynchronous database operation with a default CancellationToken.

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