c#-异步编程模型-代码示例

作者: wwmin_ | 来源:发表于2020-10-27 00:05 被阅读0次

c#-异步编程模型-代码示例
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Apache Spark 2.2.0 中文文档 - Struct
Apache Spark 2.2.0 中文文档 - Struct
Netty EventLoop与IO模型整理
Promise
RxSwift学习
04-Node 异步编程

异步编程，当有Task完成就执行

class Program
{
    static readonly HttpClient _client = new HttpClient
    {
        MaxResponseContentBufferSize = 1_000_000
    };
    static readonly IEnumerable<string> s_urlList = new string[] {
       "https://docs.microsoft.com",
       "https://docs.microsoft.com/aspnet/core",
       "https://docs.microsoft.com/azure",
       "https://docs.microsoft.com/azure/devops",
       "https://docs.microsoft.com/dotnet",
       "https://docs.microsoft.com/dynamics365",
       "https://docs.microsoft.com/education",
       "https://docs.microsoft.com/enterprise-mobility-security",
       "https://docs.microsoft.com/gaming",
       "https://docs.microsoft.com/graph",
       "https://docs.microsoft.com/microsoft-365",
       "https://docs.microsoft.com/office",
       "https://docs.microsoft.com/powershell",
       "https://docs.microsoft.com/sql",
       "https://docs.microsoft.com/surface",
       "https://docs.microsoft.com/system-center",
       "https://docs.microsoft.com/visualstudio",
       "https://docs.microsoft.com/windows",
       "https://docs.microsoft.com/xamarin"
    };
    static Task Main() => SumPageSizesAsync();

    private static async Task SumPageSizesAsync()
    {

        var stopwatch = Stopwatch.StartNew();
        IEnumerable<Task<int>> downloadTasksQuery = from url in s_urlList select ProcessUrlAsync(url, _client);

        List<Task<int>> downloadTasks = downloadTasksQuery.ToList();
        int total = 0;
        while (downloadTasks.Any())
        {
            Task<int> finishedTask = await Task.WhenAny(downloadTasks);
            downloadTasks.Remove(finishedTask);
            total += await finishedTask;
        }
        stopwatch.Stop();
        Console.WriteLine($"\nTotal bytes returned:  {total:#,#}");
        Console.WriteLine($"Elapsed time:          {stopwatch.Elapsed}\n");
        Console.ReadKey();
    }

    private static async Task<int> ProcessUrlAsync(string url, HttpClient client)
    {
        byte[] content = await _client.GetByteArrayAsync(url);
        Console.WriteLine($"{url,-60} {content.Length,10:#,#}");

        return content.Length;
    }
}

手动执行取消任务

class Program
{
    static readonly CancellationTokenSource s_cts = new CancellationTokenSource();

    static readonly HttpClient s_client = new HttpClient
    {
        MaxResponseContentBufferSize = 1_000_000
    };

    static readonly IEnumerable<string> s_urlList = new string[] {
        "https://docs.microsoft.com",
        "https://docs.microsoft.com/aspnet/core",
        "https://docs.microsoft.com/azure",
        "https://docs.microsoft.com/azure/devops",
        "https://docs.microsoft.com/dotnet",
        "https://docs.microsoft.com/dynamics365",
        "https://docs.microsoft.com/education",
        "https://docs.microsoft.com/enterprise-mobility-security",
        "https://docs.microsoft.com/gaming",
        "https://docs.microsoft.com/graph",
        "https://docs.microsoft.com/microsoft-365",
        "https://docs.microsoft.com/office",
        "https://docs.microsoft.com/powershell",
        "https://docs.microsoft.com/sql",
        "https://docs.microsoft.com/surface",
        "https://docs.microsoft.com/system-center",
        "https://docs.microsoft.com/visualstudio",
        "https://docs.microsoft.com/windows",
        "https://docs.microsoft.com/xamarin"
    };

    static async Task Main(string[] args)
    {
        Console.WriteLine("Application started.");
        Console.WriteLine("Press the ENTER key to cancel...\n");

        Task cancelTask = Task.Run(() =>
        {
            while (Console.ReadKey().Key != ConsoleKey.Enter)
            {
                Console.WriteLine("Press the ENTER key to cancel...");
            }
            Console.WriteLine("\nENTER key pressed: cancelling downloads.\n");
            s_cts.Cancel();
        });

        Task sumPageSizesTask = SumPageSizesAsync();

        await Task.WhenAny(new[] { cancelTask, sumPageSizesTask });

        Console.WriteLine("Application ending.");
    }

    private static async Task SumPageSizesAsync()
    {
        var stopwatch = Stopwatch.StartNew();
        int total = 0;
        foreach (string url in s_urlList)
        {
            int contentLength = await ProcessUrlAsync(url, s_client, s_cts.Token);
            total += contentLength;
        }

        stopwatch.Stop();
        Console.WriteLine($"\nTotal bytes returned:  {total:#,#}");
        Console.WriteLine($"Elapsed time:          {stopwatch.Elapsed}\n");
    }

    private static async Task<int> ProcessUrlAsync(string url, HttpClient client, CancellationToken token)
    {
        HttpResponseMessage response = await client.GetAsync(url, token);
        byte[] content = await response.Content.ReadAsByteArrayAsync();
        Console.WriteLine($"{url,-60} {content.Length,10:#,#}");

        return content.Length;
    }
}

超时取消任务

class Program
{
    static readonly CancellationTokenSource s_cts = new CancellationTokenSource();

    static readonly HttpClient s_client = new HttpClient
    {
        MaxResponseContentBufferSize = 1_000_000
    };

    static readonly IEnumerable<string> s_urlList = new string[]
    {
        "https://docs.microsoft.com",
        "https://docs.microsoft.com/aspnet/core",
        "https://docs.microsoft.com/azure",
        "https://docs.microsoft.com/azure/devops",
        "https://docs.microsoft.com/dotnet",
        "https://docs.microsoft.com/dynamics365",
        "https://docs.microsoft.com/education",
        "https://docs.microsoft.com/enterprise-mobility-security",
        "https://docs.microsoft.com/gaming",
        "https://docs.microsoft.com/graph",
        "https://docs.microsoft.com/microsoft-365",
        "https://docs.microsoft.com/office",
        "https://docs.microsoft.com/powershell",
        "https://docs.microsoft.com/sql",
        "https://docs.microsoft.com/surface",
        "https://docs.microsoft.com/system-center",
        "https://docs.microsoft.com/visualstudio",
        "https://docs.microsoft.com/windows",
        "https://docs.microsoft.com/xamarin"
    };
    static async Task Main(string[] args)
    {
        Console.WriteLine("Application started.");

        try
        {
            s_cts.CancelAfter(3500);

            await SumPageSizesAsync();
        }
        catch (TaskCanceledException)
        {
            Console.WriteLine("\nTasks cancelled: timed out.\n");
        }

        Console.ReadKey();
    }

    static async Task SumPageSizesAsync()
    {
        var stopwatch = Stopwatch.StartNew();

        int total = 0;
        foreach (string url in s_urlList)
        {
            int contentLength = await ProcessUrlAsync(url, s_client, s_cts.Token);
            total += contentLength;
        }

        stopwatch.Stop();

        Console.WriteLine($"\nTotal bytes returned:  {total:#,#}");
        Console.WriteLine($"Elapsed time:          {stopwatch.Elapsed}\n");
    }

    static async Task<int> ProcessUrlAsync(string url, HttpClient client, CancellationToken token)
    {
        HttpResponseMessage response = await client.GetAsync(url, token);
        byte[] content = await response.Content.ReadAsByteArrayAsync();
        Console.WriteLine($"{url,-60} {content.Length,10:#,#}");

        return content.Length;
    }
}

异步文件读写

class Program
{
    static async Task Main(string[] args)
    {
        Console.WriteLine("Hello World!");
        await SimpleWriteAsync();
        await ProcessWriteAsync();
        await SimpleReadAsync();
        await ProcessReadAsync();
        await SimpleParalleWriteAsync();
        await ProcessMultpleWritesAsync();
        Console.ReadKey();
    }
    #region 写入文本-简单示例
    /// <summary>
    /// 简单示例
    /// </summary>
    /// <returns></returns>
    public static async Task SimpleWriteAsync()
    {
        string filePath = "simple.txt";
        string text = $"Hello World";

        await File.WriteAllTextAsync(filePath, text);
    }
    #endregion
    #region 写入文本-有限控制示例
    public static async Task ProcessWriteAsync()
    {
        string filePath = "temp.txt";
        string text = $"Hello World{Environment.NewLine}";

        await WriteTextAsync(filePath, text);
    }

    private static async Task WriteTextAsync(string filePath, string text)
    {
        byte[] encodedText = Encoding.Unicode.GetBytes(text);

        using var sourceStream = new FileStream(filePath, FileMode.Create, FileAccess.Write, FileShare.None, bufferSize: 4096, useAsync: false);

        await sourceStream.WriteAsync(encodedText, 0, encodedText.Length);
    }
    #endregion
    #region 读取文本-简单示例
    public static async Task SimpleReadAsync()
    {
        string filePath = "simple.txt";
        string text = await File.ReadAllTextAsync(filePath);
        Console.WriteLine(text);
    }
    #endregion
    #region 读取文本-有限控制示例
    public static async Task ProcessReadAsync()
    {
        try
        {
            string filePath = "temp.txt";
            if (File.Exists(filePath) != false)
            {
                string text = await ReadTextAsync(filePath);
                Console.WriteLine(text);
            }
            else
            {
                Console.WriteLine($"file not found: {filePath}");
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
    }

    private static async Task<string> ReadTextAsync(string filePath)
    {
        using var sourceStream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize: 4096, useAsync: true);
        var sb = new StringBuilder();
        byte[] buffer = new byte[0x1000];
        int numRead;
        while ((numRead = await sourceStream.ReadAsync(buffer, 0, buffer.Length)) != 0)
        {
            string text = Encoding.Unicode.GetString(buffer, 0, numRead);
            sb.Append(text);
        }

        return sb.ToString();
    }
    #endregion
    #region 并行异步 I/O-简单示例
    public static async Task SimpleParalleWriteAsync()
    {
        string folder = Directory.CreateDirectory("tempfolder").Name;
        IList<Task> writeTaskList = new List<Task>();

        for (int index = 0; index < 20; index++)
        {
            string fileName = $"file-{index:00}.txt";
            string filePath = $"{folder}/{fileName}";
            string text = $"In file {index}{Environment.NewLine}";

            writeTaskList.Add(File.WriteAllTextAsync(filePath, text));
        }

        int total = 1;
        while (writeTaskList.Any())
        {

            Task finishedTask = await Task.WhenAny(writeTaskList);
            writeTaskList.Remove(finishedTask);
            await finishedTask;
            Console.WriteLine($"已完成：{total++}");
        }
        Console.WriteLine("全部完成");
        //await Task.WhenAll(writeTaskList);
    }
    #endregion
    #region 并行异步 I/O-有限控制示例
    public static async Task ProcessMultpleWritesAsync()
    {
        IList<FileStream> sourceStreams = new List<FileStream>();
        try
        {
            string folder = Directory.CreateDirectory("tempfolder").Name;
            IList<Task> writeTaskList = new List<Task>();
            for (int index = 0; index < 100; index++)
            {
                string fileName = $"file-{index:00}.txt";
                string filePath = $"{folder}/{fileName}";
                string text = $"In file {index}{Environment.NewLine}";
                byte[] encodedText = Encoding.Unicode.GetBytes(text);
                var sourceStream = new FileStream(filePath, FileMode.Create, FileAccess.Write, FileShare.None, bufferSize: 4096, useAsync: true);

                Task writeTask = sourceStream.WriteAsync(encodedText, 0, encodedText.Length);
                sourceStreams.Add(sourceStream);

                writeTaskList.Add(writeTask);
            }

            int total = 1;
            while (writeTaskList.Any())
            {
                Task finishedTask = await Task.WhenAny(writeTaskList);
                await finishedTask;
                writeTaskList.Remove(finishedTask);
                Console.WriteLine($"已完成：{total++:00}");
            }

            Console.WriteLine("全部完成");
            //await Task.WhenAll(writeTaskList);
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {
            foreach (FileStream sourceStream in sourceStreams)
            {
                sourceStream.Close();
            }
        }
    }
    #endregion
}

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