winform chart控件单点标注

没实现

参考链接（前三条有点跑题，但我也许能用上）：
​​​https://zhidao.baidu.com/question/433674777678342524.html​​​​​​

​​https://wenku.baidu.com/view/3821f41680c4bb4cf7ec4afe04a1b0717fd5b3e4.html​​​​​​

​​https://docs.microsoft.com/zh-cn/samples/browse/?redirectedfrom=MSDN-samples​​

​​http://www.luofenming.com/show.aspx?id=ART2018103000001​​

C# Coding Style
​​​https://github.com/dotnet/corefx/blob/master/Documentation/coding-guidelines/coding-style.md​​

橘子Jane