ReportProgressChanged没有更新UI

我试图通过使用多线程来更新writeablebitmap，但是我没有设法获得ProgressChanged事件触发对UI的任何更改。它虽然在边缘，因为一旦RunWorkerCompleted事件被调用UI更新。我是否没有理解ProgressChanged活动的目的，还是出了什么问题?

progresschanged的代码如下:

    private void BgWorkerMap_ProgressChanged_Handler(object sender, ProgressChangedEventArgs progressChangedArgs)
    {
        TestBitmap[7].Wb.AddDirtyRect(new Int32Rect(args[7].BgWorkerProperties.ProccessedX, args[7].BgWorkerProperties.ProccessedY, 256, 256));
        TestBitmap[7].Wb.Unlock();
        Src = TestBitmap[7].Wb;
        TestBitmap[7].Wb.Lock();
    }

这里是我使用的完整代码。如果你尝试一下，你会看到在3秒后UI将被更新(添加了一个线程睡眠1000ms/循环)

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.ComponentModel;
using System.Runtime.CompilerServices;
using System.Threading;
namespace Testmultithredabitmap
{

public partial class MainWindow : INotifyPropertyChanged
{
    private readonly BackgroundWorker worker;
    private readonly Random random = new Random();
    private WriteableBitmap src;
    public WriteableBitmap Src
    {
        get { return src; }
        set
        {
            if (Equals(value, src)) return;
            src = value;
            NotifyPropertyChanged("Src");
        }
    }
    private class WorkerArgs
    {
        public int Width { get; set; }
        public int Height { get; set; }
        public IntPtr BackBuffer { get; set; }
    }
    WorldMapFloor[] TestBitmap = new WorldMapFloor[14];
    public MainWindow()
    {
        InitializeComponent();
        DataContext = this;
        Src = new WriteableBitmap(256, 256, 96, 96, PixelFormats.Bgr32, null);
        for (int i = 0; i < TestBitmap.Length; i++)
        {
            TestBitmap[i] = new WorldMapFloor(i);
            TestBitmap[i].Wb.Lock();
        }
        worker = new BackgroundWorker();
        worker.WorkerReportsProgress = true;
        worker.DoWork += WorkerOnDoWork;
        worker.ProgressChanged += BgWorkerMap_ProgressChanged_Handler;
        worker.RunWorkerCompleted += WorkerOnRunWorkerCompleted;
        worker.RunWorkerAsync(TestBitmap);
    }
    private void WorkerOnRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs runWorkerCompletedEventArgs)
    {
        TestBitmap[7].Wb.AddDirtyRect(new Int32Rect(0, 0, 256 * 3, 256));
        TestBitmap[7].Wb.Unlock();
        Src = TestBitmap[7].Wb;
        //TestBitmap[7].Wb.Lock();
    }
    private void WorkerOnDoWork(object sender, DoWorkEventArgs doWorkEventArgs)
    {
        WorldMapFloor[] args = (WorldMapFloor[])doWorkEventArgs.Argument;
        var width = args[7].BgWorkerProperties.Stride;
        int index = 0;
        while (true)
        {
            int startXCord = (index) * 256;
            int startYCord = (0) * 256;
            int filrStartIndexInBuffer = startXCord + startYCord * 256;
            args[7].BgWorkerProperties.ProccessedX = startXCord;
            args[7].BgWorkerProperties.ProccessedY = startYCord;
            Thread.Sleep(1000);
            unsafe
            {
                var buffer = (int*)args[7].BgWorkerProperties.pBackBuffer;
                for (var x = 0; x < 256; ++x)
                {
                    for (var y = 0; y < 256; ++y)
                    {
                        buffer[filrStartIndexInBuffer + x + y * (width / 4)] = random.Next();
                    }
                }
            }
            worker.ReportProgress(0, args);
            ++index;
            if (index == 3) break;
        }
    }
    private void BgWorkerMap_ProgressChanged_Handler(object sender, ProgressChangedEventArgs progressChangedArgs)
    {
        TestBitmap[7].Wb.AddDirtyRect(new Int32Rect(args[7].BgWorkerProperties.ProccessedX, args[7].BgWorkerProperties.ProccessedY, 256, 256));
        TestBitmap[7].Wb.Unlock();
        Src = TestBitmap[7].Wb;
        TestBitmap[7].Wb.Lock();
    }
    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(string propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    public class BgWorkerMapProperties
    {
        public int ProccessedX;
        public int ProccessedY;
        public IntPtr pBackBuffer;
        public int Stride;

        public BgWorkerMapProperties(WriteableBitmap wb, int floorZ)
        {
            // Get a pointer to the back buffer. 
            pBackBuffer = wb.BackBuffer;
            Stride = wb.BackBufferStride;

        }
    }
    public class WorldMapFloor
    {
        public WriteableBitmap Wb = new WriteableBitmap(256 * 8, 256 * 8, 96, 96, PixelFormats.Bgr32, null);
        public BgWorkerMapProperties BgWorkerProperties;
        public string[] Files = null;
        public WorldMapFloor(int floorZ)
        {
            BgWorkerProperties = new BgWorkerMapProperties(Wb, floorZ);
        }
    }
}
}

感谢提前，从一个绝望的WPF程序员。