WinForms and transparency are practically incompatible. If you really need it, then switch to some other GUI framework.
– Alexander PetrovNov 22 '20 at 12:17
Maybe you will be satisfied with the [TransparencyKey](https://learn.microsoft.com/en-us/dotnet/api/system.windows.forms.form.transparencykey?view=net-5.0) property.
– Alexander PetrovNov 22 '20 at 12:20
https://stackoverflow.com/questions/16050249/transparency-for-windows-forms-textbox
– ChameeraNov 22 '20 at 12:29
See also the `DwmSetWindowAttribute()` *version* here: [How to create a semi transparent or blurred backcolor in a Windows Form](https://stackoverflow.com/a/51580871/7444103)
– JimiNov 22 '20 at 13:06