How to Correctly Use Async with ForEach in C#?

Using Async with ForEach in C#

When using the ForEach method with asynchronous operations, it's important to understand its limitations. In your code:

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

The compiler error you encounter, "The name 'Async' does not exist in the current context," indicates that you cannot use async directly within a non-asynchronous lambda expression.

Solution:

To work around this, project each element into an asynchronous operation and await them all to complete:

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

Benefits of this Approach:

• Proper Error Handling: Exceptions from async void cannot be caught, but this approach propagates them at the await Task.WhenAll line, allowing natural exception handling.
• Completion Tracking: This approach clearly indicates when the operations are complete, unlike async void, which makes this distinction difficult to track.
• Natural Syntax: GetAdminsFromGroupAsync implies the operation returns a result, making the code more intuitive and maintainable.

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