The main.cs of my project returns the following warning:
Warning 1 The type \'Extensions.MessageDetails\' in \'PATH\\Extensions.cs\'
sometimes I get this error - it's a bug though in my case.. All I have to do to fix it is change the first letter of my script file name from upper case to lowercase in the file in Explorer / (or in Unity Engine in my case) and then change the name / class accordingly in my script. Idk why this happens.. just does - and Idk why this fix works .. but in my case it always does. - Otherwise you probably have 2 copies of the same script / same class name for 2 diff scripts. Hope this helps.