https://learn.microsoft.com/ja-jp/dotnet/api/system.windows.uielement.onrender?view=netframework-4.8.1&viewFallbackFrom=windowsdesktop-10.0
UIElement.OnRender(DrawingContext) Method (System.Windows) | Microsoft Learn
When overridden in a derived class, participates in rendering operations that are directed by the layout system. The rendering instructions for this element...
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