Local Project with Nuget Package References – System.IO.FileNotFoundException

One of the features introduced with .Net Standard Projects was the definition of Nuget Package Dependecies via Package Reference tags in the csproj file and the removal of the packages.config.  There are however some issues when referring to a local project via a Project Reference using the packages.config (.Net Framework app using the legacy csproj), where the referenced project has dependencies on a Nuget Package via a Package Reference.

System.IO.FileNotFoundException: 'Could not load file or assembly 'Newtonsoft.Json, Version=12.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed' or one of its dependencies. The system cannot find the file specified.'

The dependent DLLs aren’t where the Application expects them to be because they aren’t being referenced consistently throughout the application.

Scenario

SolutionStructure
Nuget Package Reference

NugetPackageReference.Console – .Net Framework Application referencing local project NugetPackageReference.Dependent

NugetPackageReference.Dependent – .Net Standard Project referencing Nuget Package Newtonsoft.Json

DependentClass.cs – uses anything from Nuget Package

namespace NugetPackageReference.Dependent
{
    public class DependentClass
    {
        public string NewtonsoftJsonNull()
        {
            return Newtonsoft.Json.JsonConvert.Null;
        }
    }
}

 

Program.cs – calls method referring to Nuget Package

using NugetPackageReference.Dependent;

namespace NugetPackageReference.Console
{
    class Program
    {
        static void Main(string[] args)
        {
            var dependentClass = new DependentClass();

            var nullString = dependentClass.NewtonsoftJsonNull();
        }
    }
}

This will give you…

File Not Found Exception
System.IO.FileNotFoundException

Resolution

Option One – Reference Package

Add a Nuget reference to the Root Project to the missing Package.

Option Two – Migrate Packages.config to PackageReference

There is a tool in Visual Studio to migrate package references to the csproj  file, however it doesn’t currently work for all Project Types, (Service Fabric applications using .Net Framework, WPF for example).  This method is preferable.  If your project falls into this category the only way I know of to resolve the issue is Option One.

Right Click the packages.config file and select Migrate packages.config to PackageReference…

Migrate
Migrate packages.config to PackageReference

Having done this the root project will now resolve dependencies further down the tree through the PackageReferences.

Summary

Microsoft have given us a great way of migrating towards .Net Core while being able to retain business logic from existing .Net Framework applications.  The integration of these components can be complex however and initially, isn’t quite foolproof.

What issues have you faced migrating towards .Net Core?

Do you know of a better way to solve this for legacy projects?