Error cs0103: the name unityEngine don't exist in the current context

Questions & Answers
1

I have this error in monodevelop, when I write “using UnityEngine” UityEngine mark with red color, which causes you can not use autocomplete of code and display options methods to write, I think the monodevelop is not recognizing UnityEngine as library why not show me the list of methods. is a bit annoying follow the examples so, someone knows how solve it? and I have searched and have not found a concrete answer.
Thank you in advance for your time and effort.

unity version: 5.3.4

3
  1. Close Monodevelop
  2. Delete all the sln and *.*proj files in the root directory of your project.
  3. In unity double click on a script to rebuild the project

This fixed it for me.

2

I had the same problem when I updated my OS to Windows 10. In fact it turned out that .Net 3.5 had not been automatically installed and it was necessary for Monodevelop. So I installed it from the Microsoft site: Install .NET Framework 3.5 on Windows 11, 10, 8.1, 8 - .NET Framework | Microsoft Learn and it did the trick.
I hope this helps.