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Code Analyzer for C#

There is a newer version: 10.2.0.105762

Why is this an issue?
Returning null from a non-async Task/Task<TResult> method will cause a
NullReferenceException at runtime if the method is awaited. This problem can be avoided by returning Task.CompletedTask or Task.FromResult<TResult>(null)
respectively.
public Task DoFooAsync()
{
    return null;               // Noncompliant: Causes a NullReferenceException if awaited.
}

public async Task Main()
{
    await DoFooAsync();        // NullReferenceException
}

How to fix it
Instead of null Task.CompletedTask or Task.FromResult<TResult>(null)
should be returned.
Code examples
A Task returning method can be fixed like so:
Noncompliant code example
public Task DoFooAsync()
{
    return null;               // Noncompliant: Causes a NullReferenceException if awaited.
}

Compliant solution
public Task DoFooAsync()
{
    return Task.CompletedTask; // Compliant: Method can be awaited.
}

A Task<TResult> returning method can be fixed like so:
Noncompliant code example
public Task<object> GetFooAsync()
{
    return null;                          // Noncompliant: Causes a NullReferenceException if awaited.
}

Compliant solution
public Task<object> GetFooAsync()
{
    return Task.FromResult<object>(null); // Compliant: Method can be awaited.
}

Resources
Documentation

   Microsoft Learn - Task.CompletedTask Property 
   Microsoft Learn - Task.FromResult<TResult>(TResult)
  Method 

Articles & blog posts

   StackOverflow - Answer by Stephen Cleary for Is it better to return an empty task or null?
  
   StackOverflow - Answer by Stephen Cleary for Best way to handle null task inside async
  method? 
   C# Language Design - Proposal Champion "Null-conditional await"