is this true about C#?

Hi guys! So recently , I’ve been browsing through unity answers and I found the phrase; “C# in unity is the same as C# everywhere”. Is this true? And if I write the code to create a GUI box in unity into my standard C# compiler, will it give me a GUI box just like I asked for?I will be crazy happy if it’s a yes to both. Thanks!

C# as the language is the same everywhere. The libraries you use (such as Unity) are not. You cannot take your Unity GUI code and use them in a Windows Forms Application for example, because the GUI requires the engine to be running. However you can easily reuse code that doesn’t use UnityEngine.dll.