在 UWP 中使用 await Task.Run() 时引发异常 [重复]

Question

我使用了两个Task.Run。在第一个中一切正常，但在第二个中引发异常：

来自 HRESULT 的异常：0x8001010E (RPC_E_WRONG_THREAD)。

我不明白如何解决它。我想从代码中了解Task.Run 返回TextHighlighter。什么是正确的解决方案？

xaml:

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    <Grid x:Name="CommandGrid" Margin="25,50,0,50" Width="200" HorizontalAlignment="Left">
        <StackPanel x:Name="CommandStack" Orientation="Vertical">
            <Button x:Name="btnFind" Click="btnFind_Click" Content="Find Words" HorizontalAlignment="Stretch" Height="32"/>
            <TextBox x:Name="txbToFind" HorizontalAlignment="Stretch" Height="32" Margin="0,20,0,0"/>
        </StackPanel>
    </Grid>
    <Grid x:Name="BaseGrid" Margin="250,50,50,50" Background="#FFCBF3A6">
        <ScrollViewer x:Name="BaseScroll">
            <RichTextBlock x:Name="TextOneRich" Margin="20,20,35,20"/>
        </ScrollViewer>
    </Grid>
</Grid>

xaml.cs：

public sealed partial class MainPage : Page
{
    public MainPage()
    {
        this.InitializeComponent();
        Paragraph paragraph = new Paragraph();
        paragraph.Inlines.Add(new Run() { Text = "Paste the text here" });
        TextOneRich.Blocks.Add(paragraph);
    }

    private async void btnFind_Click(object sender, RoutedEventArgs e)
    {
        string tofind = txbToFind.Text.ToLower();
        string completeText = string.Empty;

        for (int a = 0; a <= TextOneRich.Blocks.Count - 1; a++)
        {
            Paragraph paragraphCurrent = TextOneRich.Blocks[a] as Paragraph;
            for (int b = 0; b <= paragraphCurrent.Inlines.Count - 1; b++)
            {
                completeText += (paragraphCurrent.Inlines[b] as Run).Text;
            }
        }

        List<int> indexList = await Task.Run(async () => await DoStuffAsync(completeText, tofind)); // Works well
        TextHighlighter HighlighterAll = await Task.Run(async () => await CreateHighlighter(indexList, tofind.Length)); // Generate exception

        TextOneRich.TextHighlighters.Clear();
        TextOneRich.TextHighlighters.Add(HighlighterAll);
    }

    private async Task<TextHighlighter> CreateHighlighter(List<int> listaindex, int lenght)
    {
        TextHighlighter Higlighter = new TextHighlighter() { Foreground = new SolidColorBrush(Colors.White), Background = new SolidColorBrush(Color.FromArgb(255, 7, 58, 77)) };
        for (int a = 0; a <= listaindex.Count - 1; a++)
        {
            Higlighter.Ranges.Add(new TextRange() { StartIndex = listaindex[a], Length = lenght });
        }
        return await Task.FromResult(Higlighter);
    }

    private async Task<List<int>> DoStuffAsync(string myTxt, string toFind)
    {
        bool thereis = true;
        List<int> indexList = new List<int>();
        string remainingText = string.Empty;
        remainingText = myTxt;
        int progressiveIndex = 0;
        int index = 0;
        while (thereis)
        {
            if (remainingText.ToLower().IndexOf(toFind) != -1)
            {
                indexList.Add(remainingText.ToLower().IndexOf(toFind) + progressiveIndex);
                index = remainingText.ToLower().IndexOf(toFind) + 1;
                progressiveIndex += index;
                remainingText = remainingText.Substring(index, remainingText.Length - index);
            }
            else
            {
                thereis = false;
            }
        }
        return await Task.FromResult(indexList);
    }
}

要粘贴的文本：text。

异常截图：exception.

感谢您的帮助。

Answer 1

您的代码的一般问题是您使用Tasks 来执行不执行任何异步I/O 工作的代码。 CreateHighlighter 和 DoStuffAsync 都被称为 Task 绝对没有充分的理由。
此外，由于CreateHighlighter 正在处理UI 对象，因此更糟糕的是，因为您不在UI 上下文中（由于您使用了Task.Run），所以使用async。你的代码应该是这样的：

public sealed partial class MainPage : Page
{
    ... 
    private async void btnFind_Click(object sender, RoutedEventArgs e)
    {
        ...
        List<int> indexList = await Task.Run(DoStuff(completeText, tofind)); 
        TextHighlighter HighlighterAll = CreateHighlighter(indexList, tofind.Length);
        ...
    }

    private TextHighlighter CreateHighlighter(List<int> listaindex, int lenght)
    {
        ...
        return Higlighter;
    }

    private List<int> DoStuff(string myTxt, string toFind)
    {
        ...
        return indexList;
    }
}