The type or namespace name 'Ports' does not exist in the namespace 'System.IO' (are you missing an assembly reference?)

Question

In older versions of Unity (eg v5), I used to solve this issue by setting

Edit > Project Settings > Player > PC setting (icon) > Other Settings > API Compatibility Level

from .Net 2.0 Subset to .Net 2.0

but in Unity 2018.3.2f1, this doesn't solve the issue. I also set the same setting to .Net 4.x but it didn't help.

Note 1 : My build settings is set to Android platform but I need SerialPort class from System.IO.Ports namespace in order to read the serial port while running the game in the Unity Editor (PC). I have done this before with Unity 5.

Note 2 : I cannot manually add a reference to the related assembly in the Visual Studio project made by Unity. The command is removed.

Answer 1

Go to Edit->projectsettings->Player->APIcompetibilityLevel = .Net4.x This worked for me.

check out this -> The type or namespace name 'Ports' does not exist in the namespace 'System.IO'

Answer 2

I came up with a workaround:

1. Switch the platform to PC: File > Build Settings > (select) PC > 'Switch Platform' button.
2. Go to Visual Studio and Build > Build Solution .
3. Switch back to Android: File > Build Settings > (select) Android >'Switch Platform' button.

By doing that, Unity adds the required assembly to 'Assembly-CSharp-Editor' project (which is related to running game inside Unity Editor).