rspec/rules/S3168/csharp/rule.adoc

An ``++async++`` method with a ``++void++`` return type is a "fire and forget" method best reserved for event handlers because there's no way to wait for the method's execution to complete and respond accordingly. There's also no way to ``++catch++`` exceptions thrown from the method.


Having an ``++async void++`` method that is not an event handler could mean your program works some times and not others because of timing issues. Instead, ``++async++`` methods should return ``++Task++``.


This rule raises an issue when non-event handler methods are both ``++async++`` and ``++void++``.


== Noncompliant Code Example

----
class HttpPrinter
{
  private string content;

  public async void CallNetwork(string url) //Noncompliant
  {
    var client = new HttpClient();
    var response = await client.GetAsync(url);
    content = await response.Content.ReadAsStringAsync();
  }

  public async Task PrintContent(string url)  // works correctly if web request finishes in under 1 second, otherwise content will be null
  {
    CallNetwork(url);
    await Task.Delay(1000);
    Console.Write(content);
  }
}
----


== Compliant Solution

----
class HttpPrinter
{
  private string content;

  public async Task CallNetwork(string url)
  {
    var client = new HttpClient();
    var response = await client.GetAsync(url);
    content = await response.Content.ReadAsStringAsync();
  }

  public async Task PrintContent(string url)
  {
    await CallNetwork(url); // <----- call changed here. If await is not added warning CS4014 will be triggered
    await Task.Delay(1000);
    Console.Write(content);
  }
}
----


== Exceptions

Event handlers, i.e. methods with two arguments, first one matching type ``++object++`` or name ``++sender++`` and the second being or inheriting from ``++EventArgs++``, are ignored.

Methods named as ``++OnSomething++`` are also ignored.