https://learn.microsoft.com/ja-jp/dotnet/api/system.windows.input.mouse.previewmousedown?view=netframework-4.8.1&viewFallbackFrom=windowsdesktop-10.0
Mouse.PreviewMouseDown Attached Event (System.Windows.Input) | Microsoft Learn
Occurs when any mouse button is depressed.
event systemmouseattachedwindowsinput