从Backgroundworker更改TextBlock.Inlines

Question

Is there any way to change the inlines from a BackgroundWorker?

I tried the following:

private void test()
    {
        var rows = GetDataGridRows(dgVarConfig);
        foreach (DataGridRow r in rows)
        {
            TextBlock tb = cMatchEx.GetCellContent(r) as TextBlock;

            if (!syntaxWorker.IsBusy)
                syntaxWorker.RunWorkerAsync(new KeyValuePair<TextBlock, String>(tb, tb.Text));
        }
    }

    private void syntaxWorker_DoWork(object sender, DoWorkEventArgs e)
    {
        if (e.Argument == null)
            Thread.Sleep(100);
        else
        {
            KeyValuePair<TextBlock, String> kvp = (KeyValuePair<TextBlock, String>)e.Argument;
            e.Result = new KeyValuePair<TextBlock, List<Run>>(kvp.Key, Syntax.Highlight(kvp.Value));
        }
    }


    private void syntaxWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        if (e.Result != null)
        {
            KeyValuePair<TextBlock, List<Run>> kvp = (KeyValuePair<TextBlock, List<Run>>)e.Result;
            TextBlock tb = kvp.Key;
            tb.Text = "";
            kvp.Value.ForEach(x => tb.Inlines.Add(x));
        }
    }

And the syntax class:

public static class Syntax
{
    static Regex subFormula = new Regex(@"\w+\(\)");
    static Regex sapFormula = new Regex(@"\w+\(([^)]+)\)");
    static Regex strings = new Regex(@"\'[^']+\'");
    static Regex numerals = new Regex(@"\b[0-9\.]+\b");
    static Regex characteristic = new Regex(@"(?:)?\w+(?:)?");
    static Regex andOr = new Regex(@"( and )|( AND )|( or )|( OR )");
    static Regex not = new Regex(@"(not )|(NOT )");

    private static Brush[] colorArray;

    public static List<Run> Highlight(String input)
    {


        colorArray = new Brush[input.Length];

        for (int i = 0; i < input.Length; i++)
            colorArray[i] = Brushes.Black;

        //Reihenfolge beibehalten!!
        assignColor(Brushes.Blue, characteristic.Matches(input));
        assignColor(Brushes.Black, andOr.Matches(input));
        assignColor(Brushes.Black, numerals.Matches(input));
        assignColor(Brushes.Orange, strings.Matches(input));
        assignColor(Brushes.DeepPink, subFormula.Matches(input));
        assignColor(Brushes.Green, sapFormula.Matches(input));
        assignColor(Brushes.Green, not.Matches(input));


        int index = 0;

        List<Run> runList = new List<Run>();

        foreach (Char character in input)
        {
            runList.Add(new Run(character.ToString()) { Foreground = colorArray[index] });
            index++;
        }


        colorArray = null;
        return runList;
    }

    public static void Check(TextBlock textBlock)
    {

    }


    private static void assignColor(Brush brush, MatchCollection matchCollection)
    {
        foreach (Match match in matchCollection)
        {
            int start = match.Index;
            int end = start + match.Length;

            for (int i = start; i < end; i++)
            {
                colorArray[i] = brush;
            }
        }
    }
}

I alway get this error: The calling thread cannot access this object because a different thread owns it.

I tried many different things: return the runList with progress changed, changed the static syntax class to a normal class.. but nothing worked, its always the same error.

I also tried to invoke it from the Backgroundworker.. that means call

    List<Run> runList = Syntax.Highlight(kvp.Value);

this.Dispatcher.Invoke((Action)(() =>
    {
        runList.ForEach(x => publicRunList.Add(x));
    }));

Anybody knows the problem?

Answer 1

Use

tb.Dispatcher.Invoke(() => {
    tb.Text = "";
    kvp.Value.ForEach(x => tb.Inlines.Add(x));
});

instead of

tb.Text = "";
kvp.Value.ForEach(x => tb.Inlines.Add(x));

Gui elements can only be accessed from the Gui thread. Using Dispatcher.Invoke ensures that the invoked action runs on it.

You are also creating Run objects in Syntax.Highlight . You also have to create Gui elements on the Gui thread. So you should also wrap this call in a dispatcher invoke:

e.Result = new KeyValuePair<TextBlock, List<Run>>(kvp.Key, Syntax.Highlight(kvp.Value));

This should work:

//this runs synchronously
kvp.Key.Dispatcher.Invoke(() => {
    e.Result = new KeyValuePair<TextBlock, List<Run>>(kvp.Key, Syntax.Highlight(kvp.Value));
});

//this runs asynchronously
kvp.Key.Dispatcher.BeginInvoke((Action)(() => {
    e.Result = new KeyValuePair<TextBlock, List<Run>>(kvp.Key, Syntax.Highlight(kvp.Value));
}));

This probably defeats the purpose of why you wanted to use a BackgroundWorker in the first place. I'd suggest to change the interface of Syntax.Highlight to return a list of tuples with the string and the highlight color instead, and then create the Run objects on the Gui thread.

Edit :

As Gopichandar noted, using BeginInvoke executes the given Action asynchronously, so that would solve the freezing of the application. It would still take a couple of seconds until all elements are added to the Gui though.

Answer 2

In WPF, only the thread that the UI element belongs to (ie the UI thread) can communicate with it. The DoWork part of the BackgroundWorker is executed in a different thread and thus cannot do anything UI-related. The same thing goes for Timers instead of BackgroundWorkers.

But if you create the BackgroundWorker with var worker = new BackgroundWorker {WorkerReportsProgress = true}; then you can set an event handler for ProgressChanged . Inside your _DoWork() , you can then say: (sender as BackgroundWorker).ReportProgress , which will call your ProgressChanged event handler in the original thread, where you can manipulate the UI elements.

Full example: http://www.wpf-tutorial.com/misc/multi-threading-with-the-backgroundworker/