Can Async Operations Be Used with ForEach, and What's the Best Alternative?

Utilizing Async within ForEach

Question:

Is it feasible to employ async functionality within the context of ForEach? A code snippet depicting the attempted implementation is provided below:

using (DataContext db = new DataLayer.DataContext())
{
    db.Groups.ToList().ForEach(i => async {
        await GetAdminsFromGroup(i.Gid);
    });
}

However, upon execution, the following error arises:

The name 'Async' does not exist in the current context

Note that the method encapsulating the using statement has been designated as async.

Answer:

The implementation of ForEach employed by List is not inherently compatible with async functionality (similar to LINQ-to-objects).

For this specific scenario, it is advised to pursue an alternative approach. This involves projecting each element into an asynchronous operation. Subsequently, the completion of these operations can be awaited asynchronously.

using (DataContext db = new DataLayer.DataContext())
{
    var tasks = db.Groups.ToList().Select(i => GetAdminsFromGroupAsync(i.Gid));
    var results = await Task.WhenAll(tasks);
}

This approach offers several advantages over utilizing an async delegate with ForEach:

• Enhanced Error Handling: Exceptions originating from async void operations cannot be handled with catch. Alternatively, this method will propagate exceptions at the line where Task.WhenAll is awaited, enabling natural exception handling capabilities.
• Completion Visibility: The conclusion of the tasks is readily discernible at the conclusion of this method owing to the employment of Task.WhenAll. In contrast, async void operations lack a straightforward means of determining completion.
• Natural Syntax: This approach aligns with the natural syntax for retrieving results. GetAdminsFromGroupAsync implies an operation that yields a result (the administrators), making this code more intuitive when such operations can return their findings rather than relying on side effects to set values.

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