Question

我有一个C＃WPF程序，它打开一个文件，逐行读取，操作每一行然后将该行写入另一个文件。那部分工作正常。我想添加一些进度报告，因此我将方法设为异步并使用等待进度报告。进度报告非常简单 - 只需更新屏幕上的标签即可。这是我的代码：

async void Button_Click(object sender, RoutedEventArgs e)
{
    OpenFileDialog openFileDialog = new OpenFileDialog();
    openFileDialog.Title = "Select File to Process";
    openFileDialog.ShowDialog();
    lblWaiting.Content = "Please wait!";
    var progress = new Progress<int>(value => { lblWaiting.Content = "Waiting "+ value.ToString(); });
    string newFN = await FileProcessor(openFileDialog.FileName, progress);
    MessageBox.Show("New File Name " + newFN);
} 

static async private Task<string> FileProcessor(string fn, IProgress<int> progress)
{
    FileInfo fi = new FileInfo(fn);
    string newFN = "C:\temp\text.txt";

    int i = 0;

    using (StreamWriter sw = new StreamWriter(newFN))
    using (StreamReader sr = new StreamReader(fn))
    {
        string line;

        while ((line = sr.ReadLine()) != null)
        {
            //  manipulate the line 
            i++;
            sw.WriteLine(line);
            // every 500 lines, report progress
            if (i % 500 == 0)
            {
                progress.Report(i);
            }
        }
    }
    return newFN;
}

非常感谢任何帮助，建议或建议。

Answer 1

将方法标记为async对执行流程几乎没有任何影响，因为您从未产生执行权。

使用ReadLineAsync代替ReadLine和WriteLineAsync代替WriteLine：

static async private Task<string> FileProcessor(string fn, IProgress<int> progress)
{
    FileInfo fi = new FileInfo(fn);
    string newFN = "C:\temp\text.txt";

    int i = 0;

    using (StreamWriter sw = new StreamWriter(newFN))
    using (StreamReader sr = new StreamReader(fn))
    {
        string line;

        while ((line = await sr.ReadLineAsync()) != null)
        {
            //  manipulate the line 
            i++;
            await sw.WriteLineAsync(line);
            // every 500 lines, report progress
            if (i % 500 == 0)
            {
                progress.Report(i);
            }
        }
    }
    return newFN;
}

这将产生UI线程并允许重新绘制标签。

PS。编译器应该使用您的初始代码发出警告，因为您使用的async方法不使用await。

异步等待进度报告不起作用

1 个答案: