我有一个在 winform 中使用实时图表的饼图，并且我尝试使用文档中的代码将工具提示更改为当前悬停：
pieChart1.DataTooltip.SelectionMode = LiveCharts.TooltipSelectionMode.OnlySender;
但是我收到以下错误： 严重性代码 描述 项目文件行抑制状态
'UserControl' does not contain a definition for 'SelectionMode' and no accessible extension method 'SelectionMode' accepting a first argument of type 'UserControl' could be found (are you missing a using directive or an assembly reference?)
我不确定我错过了什么？下面的代码是我用来绘制饼图的代码。
Func<ChartPoint, string> labelPoint = chartPoint =>
string.Format("${0:n}", chartPoint.Y, chartPoint.Participation);
SeriesCollection series = new SeriesCollection();
//reads in a data table and creates a pie series for each data row
foreach (DataRow dr in dt.Rows) …我有以下选择语句，在该语句中，我尝试以特定方式（尤其是部门的层次结构）对结果进行排序。但是，当我添加案例时，我的ORDER BY停止工作并给我一个错误：
如果语句包含UNION，INTERSECT或EXCEPT运算符，则ORDER BY项目必须出现在选择列表中。
我不知道为什么会这样，因为我在每个SELECT语句中都选择了所有内容。
Select * FROM AccountAdminTable Where CollegeCode = 'A10' AND AdminLevel LIKE 'Account Administrator'
Union
Select * FROM AccountAdminTable Where CollegeCode = 'A10' AND AdminLevel LIKE 'Department Head/Director'
Union
Select * FROM AccountAdminTable Where CollegeCode = 'A10' AND AdminLevel LIKE 'Dean/Vice President'
Order By AdminLevel ASC
这不起作用：
Select * FROM AccountAdminTable Where CollegeCode = 'A' AND AdminLevel LIKE 'Account Administrator'
Union
Select * FROM AccountAdminTable Where CollegeCode = 'A' AND AdminLevel LIKE 'Department Head/Director'
Union
Select …