Question

Using the Silverlight 4 toolkit chart control, I am trying to create a chart 100% at runtime with no evidence of it anywhere in the XAML. To do so, I create the blank chart when the page loads:

        Chart TrendChart = new Chart();
        TrendChart.Name = "TrendChart";
        TrendChart.Title = "Call History";
        TrendChart.HorizontalContentAlignment = System.Windows.HorizontalAlignment.Stretch;
        TrendChart.HorizontalAlignment = System.Windows.HorizontalAlignment.Stretch;
        TrendChart.VerticalAlignment = System.Windows.VerticalAlignment.Stretch;
        TrendChart.VerticalContentAlignment = System.Windows.VerticalAlignment.Stretch;

        GridPanel.Children.Add(TrendChart);

After the user clicks on a button to retrieve data, a List is created of this custom class:

    private class PhoneTrendDataPoint
    {
        public string XValue { get; set; }
        public double YValue { get; set; }
    }

I use that List, called CurrentCallTrends, as an ItemsSource for my chart.

        // Update the chart with the received data
        Chart TrendChart = (Chart)this.FindName("TrendChart");

        // Wipe out previous chart data
        TrendChart.Series.Clear();



        // set the data
        ColumnSeries columnSeries = new ColumnSeries();
        columnSeries.Name = "Current Call Volume";
        columnSeries.ItemsSource = CurrentCallTrends;
        //columnSeries.SetBinding(ColumnSeries.ItemsSourceProperty, new Binding("CurrentCallTrends"));
        columnSeries.DependentValueBinding = new Binding("XValue");
        columnSeries.IndependentValueBinding = new Binding("YValue");
        TrendChart.Series.Add(columnSeries);

The problem is that I get a runtime error where it prompts me to open a debugger regarding an object reference not set to an instance of an object. If I comment the line to .SetBinding then the ItemsSource vanishes and no data shows up, but at least there is no runtime error.

What am I missing?

Answer 1

After additional Googling, I made some modifications that seem to work but don’t strike me as the best way to go about doing this. Data now shows up, but I will not accept this as the answer unless there is no better method:

        // Update the chart with the received data
        Chart TrendChart = (Chart)this.FindName("TrendChart");

        // Wipe out previous chart data
        TrendChart.Series.Clear();


        // test data
        KeyValuePair<string, double>[] CurrentCallData = new KeyValuePair<string, double>[CurrentCallTrends.Count];
        for (int i = 0; i < CurrentCallTrends.Count; i++)
        {
            CurrentCallData[i] = new KeyValuePair<string, double>(CurrentCallTrends[i].XValue, CurrentCallTrends[i].YValue);
        }



        // set the data
        ColumnSeries columnSeries = new ColumnSeries();
        columnSeries.Name = "CurrentCallVolume";
        columnSeries.Title = "Current Call Volume";
        columnSeries.SetBinding(ColumnSeries.ItemsSourceProperty, new Binding());
        //columnSeries.ItemsSource = CurrentCallTrends;
        columnSeries.ItemsSource = CurrentCallData;
        columnSeries.DependentValueBinding = new Binding("Value");
        columnSeries.IndependentValueBinding = new Binding("Key");
        TrendChart.Series.Add(columnSeries);

        //this.DataContext = CurrentCallTrends;