CriticalFile-scopeC# Plug & play

Avoid Blocking Calls to Async Methods

Blocking async methods with .Result or .Wait() can cause deadlocks and prevent efficient asynchronous execution. Use await instead for proper async behavior.

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Why this matters

Blocking async methods with .Result or .Wait() can cause deadlocks and prevent efficient asynchronous execution. Use await instead for proper async behavior.

Bad vs. good

Side-by-side examples engineers can pattern-match during review.

Avoid

public static class DeadlockDemo
{
    private static async Task DelayAsync()
    {
        await Task.Delay(1000);
    }

    // This method causes a deadlock when called in a GUI or ASP.NET context.
    public static void Test()
    {
        // Start the delay.
        var delayTask = DelayAsync();
        // Wait for the delay to complete.
        delayTask.Wait(); // Noncompliant
    }
}

Prefer

public static class DeadlockDemo
{
    private static async Task DelayAsync()
    {
        await Task.Delay(1000);
    }

    public static async Task TestAsync()
    {
        // Start the delay.
        var delayTask = DelayAsync();
        // Wait for the delay to complete.
        await delayTask;
    }
}

Related rules

From the same buckets as this rule.

Critical
Do Not Call `wait()` When Holding Multiple Locks
Ensure that `wait()` is not called while holding multiple locks to prevent deadlocks.
concurrency-safety
High
Avoid Using Mutable Global Variables
Identify global variables that are mutable (e.g., lists, dictionaries). Global mutable state can cause unpredictable behavior. Recommend using local variables or encapsulating state in a class.
concurrency-safetymaintainability+1
High
Await async operations properly
Await Tasks instead of blocking (no .Result or .Wait()); prefer async/await end-to-end and configure awaits appropriately.
concurrency-safetyerror-handling

Bad vs. good

Side-by-side examples engineers can pattern-match during review.

Avoid

public static class DeadlockDemo
{
    private static async Task DelayAsync()
    {
        await Task.Delay(1000);
    }

    // This method causes a deadlock when called in a GUI or ASP.NET context.
    public static void Test()
    {
        // Start the delay.
        var delayTask = DelayAsync();
        // Wait for the delay to complete.
        delayTask.Wait(); // Noncompliant
    }
}

Prefer

public static class DeadlockDemo
{
    private static async Task DelayAsync()
    {
        await Task.Delay(1000);
    }

    public static async Task TestAsync()
    {
        // Start the delay.
        var delayTask = DelayAsync();
        // Wait for the delay to complete.
        await delayTask;
    }
}

Related rules

From the same buckets as this rule.

Critical

Do Not Call `wait()` When Holding Multiple Locks

Ensure that `wait()` is not called while holding multiple locks to prevent deadlocks.

concurrency-safety

High

Avoid Using Mutable Global Variables

Identify global variables that are mutable (e.g., lists, dictionaries). Global mutable state can cause unpredictable behavior. Recommend using local variables or encapsulating state in a class.

concurrency-safetymaintainability+1

High

Await async operations properly

Await Tasks instead of blocking (no .Result or .Wait()); prefer async/await end-to-end and configure awaits appropriately.

concurrency-safetyerror-handling