Question

我是Silverlight开发的新手，目前正在进入Charting领域。我一直在关注几个教程，这些教程展示了使用ItemsSource（http://silverlight.net/forums/t/44166.aspx）将ColumnSeries绑定到数据源是多么容易。

我是以编程方式在画布上添加图表。

Chart BudgetChart = new Chart { Title = "budget", MaxHeight= 200, MaxWidth=500};
ColumnSeries cs = new ColumnSeries();
BudgetChart.Series.Add(cs);
cs.Title = "blarg";
cs.ItemsSource = o.Budget; //returns List<Budget>
cs.IndependentValueBinding = new System.Windows.Data.Binding("Budget");
cs.DependentValueBinding = new System.Windows.Data.Binding("Year");

此代码编译良好。但是，当我调试它时，这个错误就是抛出但是，我一直在使用ItemsSource遇到很多困难。每次我分配ItemsSource时，都会收到一条错误，指出它是Sys.InvalidOperationException：控件'Xaml1'中的ManagedRuntimeError错误＃4004：System.NullReferenceException System.NullReferenceException：对象未设置为对象的实例。在System.Windows.Control.DataVisualization.Charting.ColumnSeries。＆lt;＆gt; c__DisplayClass8.b__4（）

请帮忙，这个错误让我发疯了!!!

Answer 1

尝试将ItemsSource分配移动到绑定之后。在配置其绑定后，还要将系列添加到图表中。

Chart BudgetChart = new Chart { Title = "budget", MaxHeight= 200, MaxWidth=500};
ColumnSeries cs = new ColumnSeries();
cs.Title = "blarg";
cs.IndependentValueBinding = new System.Windows.Data.Binding("Budget");
cs.DependentValueBinding = new System.Windows.Data.Binding("Year");

BudgetChart.Series.Add(cs);

cs.ItemsSource = o.Budget; //returns List<Budget>

Answer 2

确保您的第一个数据点在从属值中不包含null / Nothing。当图表试图“嗅探”所需的从属轴类型时会发生错误，并且失败。

   at System.Windows.Controls.DataVisualization.Charting.DataPointSeriesWithAxes.GetAxes(DataPoint firstDataPoint, Func`2 independentAxisPredicate, Func`1 independentAxisFactory, Func`2 dependentAxisPredicate, Func`1 dependentAxisFactory)

在System.Windows.Controls.DataVisualization.Charting.ColumnSeries.GetAxes（DataPoint firstDataPoint）

似乎没有解决方法。一种选择是子类化一个覆盖CanPlot（值）的LinearAxis。目前NumericAxis.CanPlot因值== null

而失败

 /// <summary>
    /// Returns a value indicating whether a value can plot.
    /// </summary>
    /// <param name="value">The value to plot.</param>
    /// <returns>A value indicating whether a value can plot.</returns>
    public override bool CanPlot(object value)
    {
        double val;
        return ValueHelper.TryConvert(value, out val);
    }

Answer 3

<toolkit:Chart Grid.Row="1" Margin="10" Name="columnChart" Grid.Column="0" Width="400" ScrollViewer.HorizontalScrollBarVisibility="Visible">
                <toolkit:Chart.Series>
                    <toolkit:ColumnSeries 
                        IndependentValueBinding="{Binding Path=Value}" 
                                     DependentValueBinding="{Binding Path=Key}" IsHitTestVisible="True" IsSelectionEnabled="True" SelectionChanged="ColumnSeries_SelectionChanged">
                    </toolkit:ColumnSeries>
                </toolkit:Chart.Series>
                <toolkit:Chart.Template>
                    <ControlTemplate TargetType="toolkit:Chart">
                        <chartingPrimitivesToolkit:EdgePanel x:Name="ChartArea">
                            <Grid Canvas.ZIndex="-1" Style="{TemplateBinding PlotAreaStyle}" />
                            <Border Canvas.ZIndex="10" BorderBrush="#FF919191" BorderThickness="1" />
                        </chartingPrimitivesToolkit:EdgePanel>
                    </ControlTemplate>
                </toolkit:Chart.Template>
                <toolkit:Chart.Axes>
                    <toolkit:LinearAxis Orientation="Y" Minimum="0" Maximum="100" Interval="10" />
                </toolkit:Chart.Axes>
            </toolkit:Chart>

List<KeyValuePair<int, string>> lkvpGraph1 = new List<KeyValuePair<int, string>> { };
            KeyValuePair<int, string> kvpGraph1 = new KeyValuePair<int, string>();

            List<string> lstJob = new List<string>();
            lstJob = lR1Acceptance.Where(r1 => r1.FCode == Facility).Select(r1 => r1.Job_No).Distinct().ToList();
            double nWeeks = Math.Round((dtToDate - dtFromDate).Days / 7.0, 0);
            nWeeks++;

            foreach (string job_no in lstJob)
            {
                int TotalSubmission = lR1Acceptance.Where(rr => rr.Job_No == job_no).Count();
                int TotalR1Accepted = lR1Acceptance.Where(rr => rr.Round_No == 1 && rr.Result == "A" && rr.Job_No == job_no).Count();
                int dAcceptance = (int)Math.Round(TotalR1Accepted * 100.0 / TotalSubmission, 0);
                if (TotalSubmission != 0)
                {
                    kvpGraph1 =
                             new KeyValuePair<int, string>(dAcceptance, job_no);
                    lkvpGraph1.Add(kvpGraph1);
                }

            }
            ((ColumnSeries)columnChart.Series[0]).ItemsSource = lkvpGraph1;

ColumnSeries来自Silverlight Charting Toolkit的问题

3 个答案: