摘要

在C#中，Channel类是.NET Core提供的一种新的生产者消费者模型。Channel类位于System.Threading.Channels命名空间下，它提供了一种异步的消息传递机制，可以用来在生产者和消费者之间传递数据。

正文

Channel类的应用场景

Channel类主要用于以下场景：

• 异步数据流处理：当我们需要在生产者和消费者之间进行异步数据传递时，可以使用Channel类。
• 多线程编程：Channel类提供了一种线程安全的方式来传递数据，可以避免在多线程环境中出现的数据竞争问题。
• 实时数据处理：当我们需要处理实时数据流时，可以使用Channel类来异步地处理数据。

一个简单例子

C#
Channel<string> channel = Channel.CreateUnbounded<string>();

public Form1()
{
    InitializeComponent();
}

/// <summary>
/// 写
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void btnTest_Click(object sender, EventArgs e)
{
    Random random = new Random();
    Task.Run(() =>
    {
        var writer = channel.Writer;
        while (true)
        {
            writer.WriteAsync(random.Next(1, 100).ToString());
            System.Threading.Thread.Sleep(1000);
        }
    });
}

/// <summary>
/// 读
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void btnRead_ClickAsync(object sender, EventArgs e)
{
    var reader = channel.Reader;
    Task.Run(async () =>
    {
        while (await reader.WaitToReadAsync())
        {
            while (reader.TryRead(out var message))
            {
                this.Invoke(() =>
                {
                    lsbData.Items.Add(message);
                });
            }
        }
    });
}

关闭 channel

C#
private void btnStop_Click(object sender, EventArgs e)
{
    //关闭Channel
    channel.Writer.Complete();
}

递归读取文件例子

C#
public partial class Form1 : Form
{
    Channel<string> channel = Channel.CreateUnbounded<string>();

    public Form1()
    {
        InitializeComponent();

    }
    private async Task ListFilesAsync(string directoryPath
        , ChannelWriter<string> writer)
    {
        await Task.Run(async () =>
        {
            foreach (var file in Directory.EnumerateFiles(directoryPath))
            {
                await writer.WriteAsync(file);
            }

            foreach (var directory in Directory.EnumerateDirectories(directoryPath))
            {
                await ListFilesAsync(directory, writer);
            }
        });
    }

    private async Task AddFilesToListBoxAsync(ChannelReader<string> reader, ListBox listBox)
    {
        await foreach (var file in reader.ReadAllAsync())
        {
            listBox.Invoke((Action)(() => listBox.Items.Add(file)));
            await Task.Delay(1);
        }
    }


    private async void btnRead_ClickAsync(object sender, EventArgs e)
    {
        var writer = channel.Writer;
        var reader = channel.Reader;

        // 开始做生产消费
        var producer = ListFilesAsync(@"D:\BaiduSyncdisk\11Test", writer);
        var consumer = AddFilesToListBoxAsync(reader, lsFiles);

        // 等待两个都完成
        await Task.WhenAll(producer, consumer);
    }
}

注：使用await Task.Delay(1);来避免UI冻结。