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Code Analyzer for C#

There is a newer version: 10.2.0.105762

Why is this an issue?
An async method with a
void return type does not follow the task asynchronous programming
(TAP) model since the return type should be Task or Task<TResult>
Doing so prevents control over the asynchronous
execution, such as:

   waiting for the execution to complete 
   catching any exception that might occur during execution 
   testing execution behavior 

Exceptions

   Methods with the EventHandler delegate signature.  Using void for EventHandler is compliant with the TAP model.  public async void button1_Click(object sender, EventArgs e)
{
  await DoSomethingAsync();
}
 
   Methods name matching On[A-Z]\w* pattern.  Some frameworks may not use the same EventHandler method signature  public async void OnClick(EventContext data)
{
  await DoSomethingAsync();
}
 

How to fix it
Update the return type of the method from void to Task.
Code examples
Noncompliant code example
private async void ThrowExceptionAsync() // Noncompliant: async method return type is 'void'
{
  throw new InvalidOperationException();
}

public void Method()
{
  try
  {
    ThrowExceptionAsync();
  }
  catch (Exception)
  {
    // The exception is never caught here
    throw;
  }
}

Compliant solution
private async Task ThrowExceptionAsync() // Compliant: async method return type is 'Task'
{
  throw new InvalidOperationException();
}

public async Task Method()
{
  try
  {
    await ThrowExceptionAsync();
  }
  catch (Exception)
  {
    // The exception is caught here
    throw;
  }
}

Resources
Documentation

   Microsoft Learn - async (C#
  Reference) 
   Microsoft Learn - Asynchronous
  programming 
   Microsoft Learn - Task
  asynchronous programming model 
   Microsoft Learn - Task Class 
   Microsoft Learn - Task<TResult>
  Class 
   Microsoft Learn - EventHandler Delegate