using System;
 
public class Test
{
    // 並列でダウンロードする処理
    private async Task<List<string>> LoadSomeDataAsync(List<string> idList)
    {
        var tasks = new List<Task<string>>();
        foreach (var id in idList)
        {
            // A:ここで並列にダウンロードできているのか？
            tasks.Add(DownloadAsync(id));
        }
 
        await Task.WhenAll(tasks);
        // B:Resultを使うとデッドロックすると聞いたけどawaitしていれば大丈夫？
        return tasks.Select(task => task.Result).ToList();
    }
 
 
    // 何かをダウンロードする処理
    private async Task<string> DownloadAsync(string id)
    {
        await Task.Delay(2000);
        return id;
    }
 
}

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