Your startup project 'project' doesn't reference Microsoft.EntityFrameworkCore.Design

Question

I'm building WPF application with the EntityFrameworkCore version 2.2.2

However, when i want to Add-Migration it output me an error...

Your startup project 'project' doesn't reference Microsoft.EntityFrameworkCore.Design. This package is required for the Entity Framework Core Tools to work. Ensure your startup project is correct, install the package, and try again.

I don't know why this is happen, because I can use it before this error come up.

This is my packages.config file

<?xml version="1.0" encoding="utf-8"?>
<packages>
  <package id="Costura.Fody" version="3.3.2" targetFramework="net461" />
  <package id="Fody" version="4.0.2" targetFramework="net461" developmentDependency="true" />
  <package id="Microsoft.CSharp" version="4.5.0" targetFramework="net461" />
  <package id="Microsoft.Data.Sqlite.Core" version="2.2.2" targetFramework="net461" />
  <package id="Microsoft.DotNet.PlatformAbstractions" version="2.1.0" targetFramework="net461" />
  <package id="Microsoft.EntityFrameworkCore" version="2.2.2" targetFramework="net461" />
  <package id="Microsoft.EntityFrameworkCore.Abstractions" version="2.2.2" targetFramework="net461" />
  <package id="Microsoft.EntityFrameworkCore.Analyzers" version="2.2.2" targetFramework="net461" />
  <package id="Microsoft.EntityFrameworkCore.Design" version="2.2.2" targetFramework="net461" />
  <package id="Microsoft.EntityFrameworkCore.Relational" version="2.2.2" targetFramework="net461" />
  <package id="Microsoft.EntityFrameworkCore.Sqlite" version="2.2.2" targetFramework="net461" />
  <package id="Microsoft.EntityFrameworkCore.Sqlite.Core" version="2.2.2" targetFramework="net461" />
  <package id="Microsoft.EntityFrameworkCore.Tools" version="2.2.2" targetFramework="net461" developmentDependency="true" />
  <package id="Microsoft.Extensions.Caching.Abstractions" version="2.2.0" targetFramework="net461" />
  <package id="Microsoft.Extensions.Caching.Memory" version="2.2.0" targetFramework="net461" />
  <package id="Microsoft.Extensions.Configuration" version="2.2.0" targetFramework="net461" />
  <package id="Microsoft.Extensions.Configuration.Abstractions" version="2.2.0" targetFramework="net461" />
  <package id="Microsoft.Extensions.Configuration.Binder" version="2.2.0" targetFramework="net461" />
  <package id="Microsoft.Extensions.DependencyInjection" version="2.2.0" targetFramework="net461" />
  <package id="Microsoft.Extensions.DependencyInjection.Abstractions" version="2.2.0" targetFramework="net461" />
  <package id="Microsoft.Extensions.DependencyModel" version="2.1.0" targetFramework="net461" />
  <package id="Microsoft.Extensions.Logging" version="2.2.0" targetFramework="net461" />
  <package id="Microsoft.Extensions.Logging.Abstractions" version="2.2.0" targetFramework="net461" />
  <package id="Microsoft.Extensions.Options" version="2.2.0" targetFramework="net461" />
  <package id="Microsoft.Extensions.Primitives" version="2.2.0" targetFramework="net461" />
  <package id="Newtonsoft.Json" version="9.0.1" targetFramework="net461" />
  <package id="Remotion.Linq" version="2.2.0" targetFramework="net461" />
  <package id="SQLitePCLRaw.bundle_green" version="1.1.12" targetFramework="net461" />
  <package id="SQLitePCLRaw.core" version="1.1.12" targetFramework="net461" />
  <package id="SQLitePCLRaw.lib.e_sqlite3.linux" version="1.1.12" targetFramework="net461" />
  <package id="SQLitePCLRaw.lib.e_sqlite3.osx" version="1.1.12" targetFramework="net461" />
  <package id="SQLitePCLRaw.lib.e_sqlite3.v110_xp" version="1.1.12" targetFramework="net461" />
  <package id="SQLitePCLRaw.provider.e_sqlite3.net45" version="1.1.12" targetFramework="net461" />
  <package id="System.Buffers" version="4.4.0" targetFramework="net461" />
  <package id="System.Collections.Immutable" version="1.5.0" targetFramework="net461" />
  <package id="System.ComponentModel.Annotations" version="4.5.0" targetFramework="net461" />
  <package id="System.Diagnostics.DiagnosticSource" version="4.5.0" targetFramework="net461" />
  <package id="System.Interactive.Async" version="3.2.0" targetFramework="net461" />
  <package id="System.Memory" version="4.5.1" targetFramework="net461" />
  <package id="System.Numerics.Vectors" version="4.4.0" targetFramework="net461" />
  <package id="System.Runtime.CompilerServices.Unsafe" version="4.5.1" targetFramework="net461" />
  <package id="System.Runtime.InteropServices.RuntimeInformation" version="4.0.0" targetFramework="net461" />
</packages>

The package is already installed.

Thanks a lot for any helps.

Answer 1

Add-Migration may be getting confused since you are using Costura to embed assemblies. Try removing costura to see if that resolves the issue.

Answer 2

I did install it using this command and it works !

I'm using .net core version 3.1.1

dotnet add package Microsoft.EntityFrameworkCore.Design --version 3.1.1