所以，基本上，我正在制作一个程序，其中25个任务将相同的随机任务写入一个文件，直到它达到一定的大小，并且我希望以0.5秒的间隔动态显示所选文件的文件大小，所以我制作了一个与Timer_Elapsed挂钩的计时器，它应该每0.5秒执行一次，并在UI上显示，我在mainWindow.xaml的文本块x：Name=“fileSize”中指定了这个UI，所以我将createTimer函数放在mainwindow.xaml.cs中的btnGo_Click函数中，这样事件将提取selectedFile的正确fileInfo。如果有任何错误的建议，我将不胜感激。我还在需要的情况下共享FileIO类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Windows;
using System.Threading;

namespace WriteFile
{
    internal class FileIO
    {
        private object _lock = new object();
        public volatile bool sizeReached = false;
        private StreamWriter sw = null;
        Mutex mut = null;

        public FileIO()
        {
            if (!Mutex.TryOpenExisting("MyMutex", out mut))
            {
                mut = new Mutex(true, "MyMutex");
                mut.ReleaseMutex();
            }
        }

        internal void WriteFile(string FilePath)
        {
            while (!sizeReached)
            {
                mut.WaitOne();
                    try
                    {
                        using (sw = new StreamWriter(FilePath, true))
                        {
                            sw.WriteLine(Guid.NewGuid());
                        }
                    }
                    catch (Exception ex)
                    {
                        MessageBox.Show("Exception: " + ex.Message);
                    }

                    finally
                    {
                        if (sw != null)
                        {
                            sw.Close();
                        }
                    }
                mut.ReleaseMutex();              
            }
        }

        internal void SizeMonitor(string FPath, int MaxSize, Task[] tasks)
        {
            FileInfo fi = null;
            while (!sizeReached)
            {
                if (File.Exists(FPath))
                {
                    fi = new FileInfo(FPath);

                    if (fi.Length >= MaxSize)
                    {
                        sizeReached = true;
                    }
                }

                if (sizeReached)
                {
                    foreach (Task task in tasks)
                    {
                        task.Wait();
                    }
                }
                Thread.Sleep(1);
            }

            MessageBox.Show(fi.Length.ToString());
            MessageBox.Show("Done");
        }
    }

}

mainWindow.xaml

<Window x:Class="WriteFile.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WriteFile"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <TextBlock x:Name="fileSize"/>
        <TextBox Name ="TargetSize"  VerticalAlignment="Center" FontSize="20">
        </TextBox>
        <Label Content="Target Size" HorizontalAlignment="Left" Margin="92,150,0,0" VerticalAlignment="Top"/>
        <Button Name ="btnGo" Content="Write to file" HorizontalAlignment="Left" Margin="92,267,0,0" VerticalAlignment="Top" Width="100" Click="btnGo_Click"/>
    </Grid>
</Window>

mainWindow.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.IO;
using Microsoft.Win32;
using System.ComponentModel;
using System.Timers;
using System.Threading;
using System.Runtime.CompilerServices;

namespace WriteFile
{
    public partial class MainWindow : Window
    {
        System.Timers.Timer timer = new System.Timers.Timer();
        Task[] tasks;
        Task MonitorTask;
        static FileIO fio = new FileIO();
        static string fPath;
        static FileInfo fileInfo;

        public MainWindow()
        {
            InitializeComponent();
            CreateTimer();
        }

        public void CreateTimer()
        {
            var timer = new System.Timers.Timer(500); // fire every 0.5 second
            timer.Enabled = true;
            timer.Elapsed += Timer_Elapsed;
        }

        private void Timer_Elapsed(object sender, ElapsedEventArgs e)
        {
            fileSize.Text = fileInfo.Length.ToString();
        }

        private void btnGo_Click(object sender, RoutedEventArgs e)
        {
            SaveFileDialog saveFileDialog = new SaveFileDialog();
            saveFileDialog.ShowDialog();
            Stream myStream;
            saveFileDialog.FilterIndex = 2;
            saveFileDialog.RestoreDirectory = true;

            if (File.Exists(saveFileDialog.FileName))
            {
                File.Delete(saveFileDialog.FileName);
            }

            if ((myStream = saveFileDialog.OpenFile()) != null)
            {
                StreamWriter sw = new StreamWriter(myStream);
                sw.Write(" your text");
                myStream.Close();
            }
            
            int NoOfTasks = 25;
            int Target = Convert.ToInt32(TargetSize.Text);

            fPath = saveFileDialog.FileName;
            tasks = new Task[NoOfTasks];

            fio.sizeReached = false;
            fileInfo = new FileInfo(fPath);

            for (int i = 0; i < NoOfTasks; i++) 
            {
                tasks[i] = new Task(() => fio.WriteFile(fPath));
                tasks[i].Start();
            }

            MonitorTask = new Task(() => fio.SizeMonitor(fPath, Target, tasks));
            MonitorTask.Start();
        }
    }
}