Some Entity Framework 5 query not working after migrating solution from VS 2012 to VS 2019

Zeng, Sheng (TBS) 1

We use EF5 in our project. The same code was working in VS 2012. After migrated solution from VS 2012 to VS 2019, some EF query got the following exception:
"System.NotSupportedException: Unable to create a constant value of type ''. Only primitive types or enumeration types are supported in this context." Does anyone have the similar experience?

Daniel Zhang-MSFT 9,621 Reputation points

2021-07-19T01:44:57.547+00:00

Hi anonymous user,
In order to find the cause of the problem more accurately and quickly, please provide some relevant codes to reproduce the problem and point out the specific code that caused the error.
Best Regards,
Daniel Zhang
Zeng, Sheng (TBS) 1 Reputation point

2021-07-24T12:50:05.407+00:00

If I put the same code in a newly created VS2019 project, then there’s no such issue. It’s very weird. What factors might affect the build result?
Daniel Zhang-MSFT 9,621 Reputation points

2021-07-27T09:03:13.057+00:00

Hi anonymous user,
As document said, support for some project types changes over time. A newer version of Visual Studio might not support certain projects at all, or it might require that you update a project so that it's no longer backwards-compatible.
The newly created project is new and contains all the necessary things. The old project may have some things that the new version needs but does not have.
Best Regards,
Daniel Zhang
Zeng, Sheng (TBS) 1 Reputation point

2021-09-28T15:08:16.917+00:00

After investigation again, I found there’s conflict between the additional “from” clause and the “Contains” method in EF query expression.

In the beginning, I thought the issue might be caused by the migration result not done correctly (using the wrong version of tooling). However, after testing the code again in a new VS 2019 project, I found the issue is still there.

I tried the same code in EF 6 in VS 2019, it can run through. That means we shouldn't use EF 5 in VS 2019.