C#, WPF -> GUI should not freeze while Updating in BackgroundWorker

Question

This is my project so far:

private void test()
    {
        var rows = GetDataGridRows(dgVarConfig);

        Dictionary<TextBlock, String> dic = new Dictionary<TextBlock, string>();
        foreach (DataGridRow r in rows)
        {
            TextBlock tb = cMatchEx.GetCellContent(r) as TextBlock;
            dic.Add(tb, tb.Text);
        }

        if (!syntaxWorker.IsBusy)
            syntaxWorker.RunWorkerAsync(dic);
    }



    private void syntaxWorker_DoWork(object sender, DoWorkEventArgs e)
    {
        if (e.Argument == null)
            Thread.Sleep(100);
        else
        {
            Dictionary<TextBlock, String> dic = (Dictionary<TextBlock, String>)e.Argument;

            foreach (KeyValuePair<TextBlock, String> kvp in dic)
            {

                kvp.Key.Dispatcher.BeginInvoke(new Action(() =>
                {
                    kvp.Key.Inlines.Clear();
                    Syntax.Highlight(kvp.Value).ForEach(x => kvp.Key.Inlines.Add(x));
                }));
            }

        }
    }

Syntax.Highlight:

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;
            }
        }
    }
}

With this code, the gui freezes for about 2 seconds. Is there any way to build up the gui step by step and avoid any freezing? Its no problem to see how its building up, just the freezing is a problem.

Hope anybody knows how to resolve this.

Answer 1

You could move a good portion of the work outside of the invoke like this :

One small caveat : i'm not entirely sure how you retreive the text of the textboxes. you might have to do a separate invoke for that (see comment in the code)

public class RunInfo
{
    public string Content { get; set;}
    public Color foreground { get; set; }
    public RunInfo(string content)
    {
        Content = content;
    }

    public Run AsRun()
    {
       return new Run(Content){ Foreground = foreground };
    }

}



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<RunInfo> 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 RunInfo(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;
            }
        }
    }
}




private void syntaxWorker_DoWork(object sender, DoWorkEventArgs e)
{
    if (e.Argument == null)
        Thread.Sleep(100);
    else
    {
        Dictionary<TextBlock, String> dic = (Dictionary<TextBlock, String>)e.Argument;

        foreach (KeyValuePair<TextBlock, String> kvp in dic)
        {
            //i am unsure if this line will work. if it does not, you might need to do a separate dispatcher invoke in order to retreive the text from the textbox.
            List<RunInfo> runinfoObjects = Syntax.Highlight(kvp.Value); 
            kvp.Key.Dispatcher.BeginInvoke(new Action(() => 
            {
                kvp.Key.Inlines.Clear();
                //we'd run into problems here, since wpf won't allow us to add elements created in a background thread. since we now make the Run object inside the invoke, we should be fine.
                runinfoObjects.ForEach(x => kvp.Key.Inlines.Add(x.AsRun()));
            }));
        }
    }
}