Is it possible to reference .net framework 4.7.2 class library from an ASP.NET Core MVC project?

Question

I have an ASP.NET MVC 5 project which works well and it also references a .NET Framework 4.7.2 Class library which produces some CrystalReports. CrystalReports does not supp

Answer 1

Chris has already provided an excellent and accurate answer but I'll try to add a bit more color by sharing the results of an experiment I did.

Experiment: I have a web application targerting .Net Core 3.1. It calls a library that targets the Full Framework. In that library I specifically make a call to a Full Framework API that is not available in .Net Core 3.1, in this case that type is SHA512Cng.

My library code is:

        /// 

        /// Returns a base64 encoded Sha512 hash of the text specified.
        /// Uses the SHA512Cng implementation to do the hashing.
        /// 
        /// 
        /// 
        public static string Sha512Hash(string text) {

            using (SHA512Cng sha512Cng = new SHA512Cng()) {
                byte[] bytes = Encoding.ASCII.GetBytes(text);
                byte[] hashButes = sha512Cng.ComputeHash(bytes);
                return Convert.ToBase64String(hashButes);
            }
        }

In the home controller of my web application I make a call to use that Library method like so:

       public IActionResult Index() {
            string hash = App.Lib.Sha512Hash("hello world");

            return View();
        }

Pretty simple experiment. This code is running on a windows machine that has the full framework installed. If I call this library from a website targeting the Full Framework it works perfectly.

When I call this method in the Library from a .Net Core 3.1 website, what happens? That's the questions I wanted this experiment to answer.

And the answer is...

It throws the following exception:

System.TypeLoadException: 'Could not load type 'System.Security.Cryptography.SHA512Cng' from assembly 'System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.'

Screenshot:

So the takeaway is this: It really doesn't matter whether your code is running on a box with the Full Framework or not. If you reference a Full Framework Library from a website targeting Asp.Net Core 3 and make a call into a method that references a type that is incompatible with Asp.Net Core 3, then it's gonna throw.