很抱歉，上次我帮不上忙。我测试了 TextAnnotation 的居中，实际上当 InnerPlotPosition 设置为 auto 时它会出现问题。此外，在link 找到的答案会在每个 PrePaint 处创建一个新的 TextAnnotation 实例，导致 TextAnnotation 重叠和居中文本模糊。
我找不到避免调整甜甜圈大小的方法（我不确定这是否可能，在这一点上......我会等待其他一些答案）但也许这可以解决解决方法。
首先我创建了一个字典来存储居中的 TextAnnotation 引用（关键是图形名称，以防你有多个），然后在 PrePaint 事件中我得到图形中使用的 TextAnnotation 的正确引用并更新那个的坐标。
其次，我手动设置了InnerPlotPosition，这似乎解决了TextAnnotation的居中问题。当然，您需要为 InnerPlot 指定坐标和大小，就像我对线条所做的那样：
chart1.ChartAreas[0].InnerPlotPosition = new ElementPosition(0, 0, 60.65f, 94.99f);
最后，我手动设置图例的位置和大小，并使用扩展方法 WrapAt 在图例项文本中的每个 _maxLegendTextBeforeWrap 设置一个“换行符”。没办法让它随着图例区域的宽度动态变化，只能手动设置。
下面是最终效果的 GIF。不知道这是否适合您作为解决方案（太多的调整和代码，以我的口味），但无论如何。也许这可以引发一些关于如何解决的新想法。
为此，我创建了这些全局变量：
/// <summary>
/// Saves the currently doughnut centered annotations per graph.
/// </summary>
private IDictionary<string, TextAnnotation> _annotationsByGraph;
/// <summary>
/// Number of characters
/// </summary>
private int _maxLegendTextBeforeWrap = 10;
/// <summary>
/// Legend area width.
/// </summary>
private int _legendWidth = 20;
/// <summary>
/// Legend area height.
/// </summary>
private int _legendHeight = 90;
这是 Load 事件的处理程序：
private void ChartTest_Load(object sender, EventArgs e)
{
// ** Start of test data **
chart1.Series["Series1"].Points.AddXY("A", 33);
chart1.Series["Series1"].Points[0].LegendText = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
chart1.Series["Series1"].Points.AddXY("B", 33);
chart1.Series["Series1"].Points[1].LegendText = "BBBBBBBBBBBBBBBBBBBB";
chart1.Series["Series1"].Points.AddXY("C", 34);
chart1.Series["Series1"].Points[2].LegendText = "CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC";
// ** End of test data **
// Creates a new instance of the dictionary storing the references to the annotations.
_annotationsByGraph = new Dictionary<string, TextAnnotation>();
// Createa a new instance of an annotation for the chart1 graph.
_annotationsByGraph.Add(chart1.Name, new TextAnnotation());
// Manually setting the position of the chart area prevents the imperfect positioning of the
// TextAnnotation at the center of the doughnut.
chart1.ChartAreas[0].Position.Auto = true;
// Manually set the position of the InnerPlotPosition area prevents the imperfect positioning of the
// TextAnnotation at the center of the doughnut.
chart1.ChartAreas[0].InnerPlotPosition.Auto = false;
chart1.ChartAreas[0].InnerPlotPosition = new ElementPosition(0, 0, 60.65f, 94.99f);
// Minimum size for the legend font.
chart1.Legends[0].AutoFitMinFontSize = 5;
// Set the legend style as column.
chart1.Legends[0].LegendStyle = LegendStyle.Column;
// Splits the legend texts with the space char every _maxLegendTextBeforeWrap characters.
chart1.Series["Series1"].Points.ToList().ForEach(p => p.LegendText = p.LegendText.WrapAt(_maxLegendTextBeforeWrap));
}
这是 PrePaint 事件的处理程序：
private void chart1_PrePaint(object sender, ChartPaintEventArgs e)
{
if (e.ChartElement is ChartArea)
{
// Get the reference to the corresponding text annotation for this chart.
// We need this, otherwise we are creating and painting a new instance of a TextAnnotation
// at every PrePaint, with the resulting blurrying effect caused by the overlapping of the text.
var ta = _annotationsByGraph[e.Chart.Name];
// Check if the annotation has already been added to the chart.
if (!e.Chart.Annotations.Contains(ta))
e.Chart.Annotations.Add(ta);
// Set the properties of the centered TextAnnotation.
ta.IsMultiline = true;
ta.Text = "Results of Calculation\nx%";
ta.Font = new Font("Candara", e.Position.Height / 10, FontStyle.Regular);
ta.Width = e.Position.Width;
ta.Height = e.Position.Height;
ta.X = e.Position.X;
ta.Y = e.Position.Y;
// Move the legend manually to the right of the doughnut.
e.Chart.Legends[0].Position = new ElementPosition(e.Position.X + e.Position.Width, e.Position.Y, _legendWidth, _legendHeight);
}
}
这就是按钮的作用：
private void BtnChangeLegendItemLength_Click(object sender, EventArgs e)
{
if (chart1.Series["Series1"].Points[1].LegendText.StartsWith("DD"))
chart1.Series["Series1"].Points[1].LegendText = "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB".WrapAt(_maxLegendTextBeforeWrap);
else
chart1.Series["Series1"].Points[1].LegendText = "DDDDDD".WrapAt(_maxLegendTextBeforeWrap);
}
这是扩展方法定义：
internal static class ExtensionMethods
{
public static string WrapAt(this string legendText, int maxLengthBeforeWrap)
{
if (legendText.Length <= maxLengthBeforeWrap)
return legendText;
// Integer division to get how many times we have to insert a space.
var times = legendText.Length / maxLengthBeforeWrap;
// Counter of added spaces.
var spacesAdded = 0;
// Iterate for each space char needed.
for (var i = 1; i <= times; i++)
{
// Insert a space char every maxLengthBeforeWrap positions.
legendText = legendText.Insert(maxLengthBeforeWrap * i + spacesAdded, new string(' ', 1));
spacesAdded++;
}
return legendText;
}
}