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Hi everyone,

I'm encountering an issue with asynchronous operations in my .NET Core application. I'm trying to fetch data from an external API and process it, but I'm seeing unexpected behavior, specifically regarding deadlocks and incorrect results.

Here's a simplified snippet of my code:

public async Task<string> GetDataAsync(string url)
{
    using (var client = new HttpClient())
    {
        var response = await client.GetStringAsync(url);
        // Some processing here
        return response;
    }
}

public void ProcessData()
{
    // This is where I suspect the problem lies
    var data = GetDataAsync("https://api.example.com/data").Result;
    Console.WriteLine(data.Length);
}

I understand that using `.Result` on an awaited task can lead to deadlocks. I've tried using `.GetAwaiter().GetResult()` as well, but the issue persists.

Could anyone shed some light on the correct way to handle this scenario in a typical ASP.NET Core web application context?

Hello John,

You're right to suspect the blocking calls like `.Result` or `.GetAwaiter().GetResult()`. In ASP.NET Core, the default synchronization context is designed to avoid deadlocks. When you block on an async method from a synchronous context that has a synchronization context, it can lead to issues.

The best practice is to make your entire call stack asynchronous. Instead of calling `GetDataAsync().Result` from `ProcessData`, you should make `ProcessData` asynchronous as well:

public async Task<string> GetDataAsync(string url)
{
    using (var client = new HttpClient())
    {
        var response = await client.GetStringAsync(url);
        // Some processing here
        return response;
    }
}

public async Task ProcessDataAsync() // Renamed and made async
{
    var data = await GetDataAsync("https://api.example.com/data"); // Use await
    Console.WriteLine(data.Length);
}

If `ProcessData` is an event handler or needs to be called from a synchronous API, consider using `Task.Run()` to offload the asynchronous work to a thread pool thread, although this should generally be a last resort.

Also, be mindful of `HttpClient` lifetime. It's recommended to use a single instance of `HttpClient` for the lifetime of your application if possible, or use `IHttpClientFactory` for better management of connections and resilience.

Alice, thank you for the quick response!

That makes a lot of sense. I was indeed trying to keep a synchronous method that called an asynchronous one, which is a common anti-pattern. Making the calling method asynchronous is the cleaner approach.

I'll refactor my code to use `async` and `await` throughout the relevant call chain. I'll also look into using `IHttpClientFactory` for managing the `HttpClient` instance properly. This is a real improvement!