在MVVM后台线程进度通知？ [英] Background thread progress notification in MVVM?

问题描述

我如何修改MVVM视图模型进度工作性质正在后台线程做了什么？

How do I modify an MVVM view model Progress property for work being done on a background thread?

我创建一个MVVM应用程序，在后台线程执行一个任务，使用 Task.Factory.StartNew（）和 Parallel.ForEach（）。我使用这篇文章作为指南。到目前为止，我的代码看起来是这样的：

I am creating an MVVM app that executes a task on a background thread, using Task.Factory.StartNew() and Parallel.ForEach(). I am using this article as a guide. So far, my code looks like this:

Task.Factory.StartNew(() => DoWork(fileList, viewModel));

其中，的fileList 是一个文件到列表进行处理，而视图模型与进度属性视图模型。在的DoWork（）方法看起来是这样的，到目前为止：

Where fileList is a list of files to be processed, and viewModel is the view model with the Progress property. The DoWork() method looks like this, so far:

private object DoWork(string[] fileList, ProgressDialogViewModel viewModel)
{
    Parallel.ForEach(fileList, imagePath => ProcessImage(imagePath));
}

的

processImage来（）方法执行实际的图像处理。视图模型的进度属性绑定到显示的后台进程开始之前在对话框的进度条。

The ProcessImage() method does the actual image processing. The view model's Progress property is bound to a progress bar in a dialog that is displayed just before the background process begins.

我想更新视图模型进度的 Parallel.ForEach（）语句的每次迭代后财产。所有我需要做的是增加的属性值。我怎么做？感谢您的帮助。

I'd like to update the view model Progress property after each iteration of the Parallel.ForEach() statement. All I need to do is increment the property value. How do I do that? Thanks for your help.

推荐答案

由于属性是一个简单的属性（而不是集合），你应该能够设置它直接。 WPF会自动处理的编组回UI线程。

Since the property is a simple property (and not a collection), you should be able to set it directly. WPF will handle the marshaling back to the UI thread automatically.

然而，为了避免出现竞争状况，你需要处理你的完成递增反击明确。这可能是这样的：

However, in order to avoid a race condition, you'll need to handle the incrementing of your "done" counter explicitly. This could be something like:

private object DoWork(string[] fileList, ProgressDialogViewModel viewModel)
{
    int done; // For proper synchronization
    Parallel.ForEach(fileList, 
       imagePath => 
       {
           ProcessImage(imagePath));
           Interlocked.Increment(ref done);
           viewModel.Progress = done;
       }
}

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