asp.net - Type "IEnumerable<>" is defined in an unreferenced assembly in MVC6?

Question

Severity Code Description Project File Line Suppressed Status
Error CS0012 . A reference to assembly "System.Runtime, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" must be added. Jiang.LEMS.Freamework..NET Framework 4.5.1 C:DocumentVisual Studio 2015ProjectsLEMSJiang.LEMS.FreameworkEFDbContext.cs 23 Activity

Answer 1

The prompt is very clear, there is a lack of references

Answer 2

Reference is missing, or the object is not instantiated.