How can I reference a class in MVC project that retrieves data from database with asp.net core

Question

I have MVC application which contains a class called DataAccess that retrieves data form a database. I added asp.Net Core application and I referenced the MVC application in the asp.Net Core application. The problem is that when I call one of the DataAccess methods and compile the solution, I get an error:

Error CS0012 The type 'DataTable' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.

See below code for my .net Core API:

using Microsoft.AspNetCore.Mvc;
using shopping;
using System.Collections.Generic;
using System.Data.Common;

    namespace ShoppingAPI.Controllers
    {
        [Route("api/[controller]")]
        public class ValuesController : Controller
        {
            // GET api/values
            [HttpGet]
            public IActionResult  Get()
            {
                DataAccess da = new DataAccess();
                da.GetDataTable("SELECT * FROM USERS;", new List<DbParameter>());
                return Ok();
            }
}

Can anyone advise me?

Answer 1

Quick Solution

Step 1. Target the correct framework

With the assumption that you are using Visual Studio 2017 here is how you can solve your problem.

1. Right-click on your project and select Edit *****.csproj

2. In the .csproj file, you need to replace the target framework to the .NET Framework.

for example:

 // incorrect <TargetFramework>netcoreapp2.0</TargetFramework> // correct <TargetFramework>net462</TargetFramework> 

source: https://docs.microsoft.com/en-us/dotnet/standard/net-standard

For a list of the Target Framework Moniker (TFM) (ie, net47 , netstandard2.0 , netcoreapp2.0 , etc.*) you can check this link out: https://docs.microsoft.com/en-us/dotnet/standard/frameworks

Step 2. Run dotnet restore

Go to your output window and run dotnet restore .

Sometimes Visual Studio may misbehave (depending on which update you have installed), so you may have to close and re-open your Visual Studio. Otherwise, sometimes a clean/re-build may do the trick.

Wnat Are We Doing?

According to your comments, you noted that you were trying to reference a project that was MVC4, which means it was likely not written using a library that is supported directly with the .NET Core framework. Instead, it would be supported by the .NET Framework (w/ .NET Core) instead.

The solution above just does that for you.