有关WPF多线程和多进程操作文件的问题

要实现的功能是   多线程创建进程（这个没办法，是调用的C++的类库）来创建图片或是修改原有图片   创建或修改后在主线程上展示图片   问题是  在没有异常出现的情况下  图片已修改完成  但没有显视 代码走到了这里this.Image.Source = bi;  但显示为空 在文件夹下可以看到修改后的图片   求解释！！！！！！！！！！！
try
            {
                Process p = new Process(); //这里是多线程操作的
                string srt = AppDomain.CurrentDomain.BaseDirectory;
                DateTime dt;
                while (listCreatImage.Count > 0)
                {
                    ForCreatImage f = listCreatImage[0];
                    try
                    {
                        if (File.Exists(f.FSTR))
                        {
                            dt = File.GetLastWriteTime(f.FSTR);
                        }
                        else
                            dt = DateTime.Now;
                        ProcessStartInfo ps = new ProcessStartInfo(srt + "ABC.dll", "-ss " + f.FTime.ToString() + " -y -i " + f.FfileName + " -s 120*90 -t 0.001 -f image2 " + f.FSTR);
                        ps.UseShellExecute = false;
                        ps.CreateNoWindow = true;
                        p.StartInfo = ps;
                        p.Start();
                    }
                    catch (Exception ex)
                    {
                        lock (listCreatImage)
                        {
                            listCreatImage.RemoveAt(0);
                        }
                        break;
                    }
                    while (dt == File.GetLastWriteTime(f.FSTR))//判断文件是否创建或是修改
                    {
                        Thread.Sleep(1000);
                    }
                    githis.Invoke(listCreatImage[0]);
                    lock (listCreatImage)
                    {//主线程会不定期的向list里面增加
                        listCreatImage.RemoveAt(0);
                    }                }
                p.Close();
                p.Dispose();            }
            catch (Exception ex)
            {
            }
            lock (o)
            {
                createImageThread.Abort();
            }
以上是创建文件或是修改文件//通过上部分的githis.Invoke(listCreatImage[0]);的实现
try
            {
                BitmapImage bi = new BitmapImage();
                FileStream fs = File.Open(imageSource, FileMode.Open);
                if (fs.CanRead)
                {
                    bi.BeginInit();
                    bi.StreamSource = fs;
                    DateTime dt = DateTime.Now;
                    
                    bi.EndInit();
                    int d = bi.PixelWidth;
                    this.Image.Source = bi;  //代码每次都会走到这里
                    fs.Close();
                    fs.Dispose();
                }
                else //从来没到这里
                { 
                }
            }
            catch (Exception)
            {
            }WPF多线程图片