Metadata

ID: csharp-best-practices/completed-task-not-null

Language: C#

Severity: Warning

Category: Best Practices

Description

This rule emphasizes the importance of always returning a Task from asynchronous methods in C#, instead of null. Returning null from an async method can lead to NullReferenceException errors at runtime when the returned task is awaited. This can make debugging more difficult and can lead to unexpected behavior or bugs in your application.

The importance of this rule stems from the fact that it’s a common best practice in asynchronous programming. It ensures that your asynchronous methods always return a valid task that can be awaited, regardless of the execution path of your method. This can make your asynchronous code easier to understand and maintain.

How to Remediate

To fix this issue, always return a completed Task or Task<T> from your asynchronous methods instead of null. You can use Task.CompletedTask to return a completed task without a result, or Task.FromResult(result) to return a completed task with a result. For example: return Task.FromResult<object>(null); This will ensure that your asynchronous methods are always returning a valid task that can be awaited.

Non-Compliant Code Examples

public class {
    Task<object> GetAsync()
    {
        return null;
    }
}

Task<object> GetAsync()
{
    return null;
}

Compliant Code Examples

Task<object> GetAsync()
{
    return Task.FromResult<object>(null);
}

Seamless integrations. Try Datadog Code Security

Datadog Code Security