异步等待进度报告不起作用

Question

我有一个C#WPF程序打开一个文件,逐行读取,操纵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;
}

任何帮助,建议或建议将不胜感激.

Answer 1

只是将您的方法标记为async对执行流程没有任何影响,因为您不会产生执行.

使用ReadLineAsync替代ReadLine和WriteLineAsync取代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线程并允许重绘标签.

PS.编译器应该使用您的初始代码发出警告,因为您有一个async不使用的方法await.