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Code Analyzer for C#

There is a newer version: 10.2.0.105762

Why is this an issue?
ValueTask<TResult> provides a value type that wraps a Task<TResult> and the corresponding TResult.
It was introduced in .NET Core 2.0 to optimize
memory allocation when functions return their results synchronously.
Using ValueTask and ValueTask<TResult> in the following ways is discouraged as it could result in a race
condition:

   Calling await multiple times on a ValueTask/ValueTask<TResult>. The wrapped object may have been
  reused by another operation. This differs from Task/Task<TResult>, on which you can await multiple times and always
  get the same result. 
   Calling await concurrently on a ValueTask/ValueTask<TResult>. The underlying object is not thread
  safe. What’s more, it has the same effect as awaiting multiple times a ValueTask/ValueTask<TResult>. This again
  differs from Task/Task<TResult>, which support concurrent await. 
   Using .Result or .GetAwaiter().GetResult() without checking if the operation is completed.
  IValueTaskSource/IValueTaskSource<TResult> implementations are not required to block until the operation completes.
  On the other hand, Task/Task<TResult> blocks the call until the task completes. 

It is recommended to use ValueTask/ValueTask<TResult> either by calling await on the function
returning it, optionally calling ConfigureAwait(false) on it, or by calling .AsTask() on it.
This rule raises an issue when the following operations are performed on a ValueTask/ValueTask<TResult> instance
unless it happens in a loop:

   Awaiting the instance multiple times. 
   Calling AsTask multiple times. 
   Using .Result or .GetAwaiter().GetResult() multiple times 
   Using .Result or .GetAwaiter().GetResult() when the operation has not yet completed 
   Using of these ways to consume the instance multiple times. 

How to fix it
Code examples
Noncompliant code example
ValueTask<int> vt = ComputeAsync();
int result = await vt;
result = await vt; // Noncompliant, variable is awaited multiple times

int value = ComputeAsync()).GetAwaiter().GetResult(); // Noncompliant, uses GetAwaiter().GetResult() when it's not known to be done

Compliant solution
ValueTask<int> vt = ComputeAsync();
int result = await vt;

int value = await ComputeAsync().AsTask();

Resources
Documentation

   ValueTask 
   ValueTask<TResult> 
   Understanding the Whys, Whats,
  and Whens of ValueTask 

Standards

   STIG Viewer - Application Security and
  Development: V-222567 - The application must not be vulnerable to race conditions.