启动项目不引用 Microsoft.EntityFrameworkCore.Design

Do you have multiple projects? If yes then you have to make the host project a startup project from solution explorer and set the project as default (which project has DBContext) in PMC. Then run the Add-Migration command.

Package Manager Console screenshot:

Try to set your web project again as startup project and this warning should go. (Right click on web project > Set as startUp project)

I found the solution here.

In short, edit your csproj file, and add to your PropertyGroup section the following entry:

<GenerateRuntimeConfigurationFiles>True</GenerateRuntimeConfigurationFiles>

I got this error because Visual Studio defaulted to using entity framework core rather than old-school entityframework for .NET Framework: entity framework 6. This was my solution:

EntityFramework\Update-Database

Or reference the version explicitly:

EntityFramework6\Update-Database

Also worth checking the right project is selected in the Package Manager Console. That likes to sneak back to other projects half the time!

If you want to do migrations without adding EF references in your services, your library with data access needs a way to construct an instance of your DbContext. You can do this by implementing IDesignTimeDbContextFactory, example:

public class MyContextFactory : IDesignTimeDbContextFactory<MyContext>
{
public MyContext CreateDbContext(string[] args)
{
var optionsBuilder = new DbContextOptionsBuilder<MyContext>();
optionsBuilder.UseSqlServer("Data Source=MyDatabase");


return new MyContext(optionsBuilder.Options);
}
}

"Your 'project name' does not refer to your startup project Microsoft.EntityFrameworkCore.Design. This package is required for the Entity Framework Core Tools to work. Make sure your startup project is correct, install the package and try again."

If you get this error, try 'Build > Clean Solution' in your project and then try running your command again.

This worked in my project. Or you may want to look at the documentation.

I use .Net Core 3.1 version in my project.

Set the project with entities as the Startup project and run the scaffolding command. it worked for me. Don't forget to revert the startup project after.

Please make sure You have installed below packages. I was also getting same error and Installed below packages and it worked for me.

Microsoft.EntityFrameworkCore.SqlServer
Microsoft.EntityFrameworkCore.Design
Microsoft.EntityFrameworkCore.Tools

In order for the migration tool to work, I had to add the Microsoft.VisualStudio.Web.CodeGeneration.Design NuGet package as well.

This happen for me when

Both Entity Framework Core and Entity Framework 6 are installed. The Entity Framework Core tools are running. Use 'EntityFramework6\Add-Migration' for Entity Framework 6.

solution was EntityFrameworkCore\Add-Migration

None of the options worked for me. But the one I tried on this topic worked: EF Core 3 design time migrations broken by Microsoft.EntityFrameworkCore.Design DevelopmentDependency

I just commented out the following after importing the package to the Data project:

<ItemGroup>
<PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="3.1.4" />
<PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="3.1.5">
<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
<!--<PrivateAssets>all</PrivateAssets>-->
</PackageReference>

Thank you so much Microsoft by breaking the existing projects every time when you release a new .NetCore update!

I had the same issue while I had more than one project in the solution. the mistake I was doing was I had not selected the concerned project as the Default project in Package Manager Console. So check if you have selected the same project as default in Package Manager Console in which you want to run migration command.

You could solve this by using below commands

dotnet tool install --global dotnet-ef
dotnet add package Microsoft.EntityFrameworkCore.Design

More a workaround than a solution, I ended up unloading the startup project from the solution. Ran the migration, added the project back to the solution. I don't expect to have many migrations, so it worked for me. What baffles me is that I have a solution with similar features and I didn't have the same issue.

There is absolutely NO reason to install Microsoft.EntityFrameworkCore.Design to your API project while having a separate Data project.

Quick solution

When using add-migration, just add a parameter to set the -StartUpProject to your Data proj (by default I presume your startup project is the API proj).

Example add-migration command below:

add-migration {migration_name} -StartUpProject {your_data_proj_name} -project {your_data_proj_name} -v

Example update-database command below:

update-database -StartUpProject {your_data_proj_name} -project {your_data_proj_name} -v

I hope this help you guys

PS: more info about the add-migration params can be found here

First install the "microsoft.entityframeworkcore.design" better to install it using the nuget from the Package Manager Console and the command is: Install-Package Microsoft.EntityFrameworkCore.Design -Version x.x.x the link to the nuget package is this link

Then rebuild the solution after installing the required DLL, you might need to install other dependencies after that, but at least you will be done with the "microsoft.entityframeworkcore.design" dependency

For anyone stuck on this issue with EF Core Design installed, I simply unloaded and reloaded the project to solve the problem.

Right click the project in the Solution Explorer, unload the project, then right click again to reload.

Now it should recognize Entity Framework Core Design.

Please make sure you have installed the same version of the packages below:

1. Microsoft.EntityFrameworkCore.SqlServer
2. Microsoft.EntityFrameworkCore.Design

I was also getting the same error and re-installed the packages with the same version and it worked for me.

What solved it for me was to have the same version of Microsoft.EntityFrameworkCore.Design and Microsoft.EntityFrameworkCore.SqlServer packages, which in my case was 2.1.14

Edit 1: This was solved using a

<Project Sdk="Microsoft.NET.Sdk.Web">

on

<TargetFramework>net5.0</TargetFramework>

There is one more reason to get this error (even if you changed PrivateAssets) - if your startup project is not referenced to data access project. So if you just created new projects it can be possible case

It works for me when i deleted Private Assets in .csproj or

Not making the private assets property all through the properties of the package

you need to install the design package of Microsoft EntityFrameworkCore. run this command

dotnet add package Microsoft.EntityFrameworkCore.Design

this will include package in .csproj file

Another cause of this is simply I was completely missing the package Microsoft.EntityFrameworkCore.Tools package, which became uninstalled somehow.

It's worth noting that the error I got for this was similar but different and was "Your target project 'XXX' doesn't reference EntityFramework. This package is required for the Entity Framework Core Tools to work. Ensure your target project is correct, install the package, and try again."

Installing it got me back on track.

Click on startup project name and remove this:

<PrivateAssets>all</PrivateAssets>

from package reference Microsoft.EntityFrameworkCore.Design.

I had this same problem and I found out that the cause was that I installed Misoft.EntityFrameworkCore, Misoft.EntityFrameworkCore.SqlServer and Misoft.EntityFrameworkCore.Tools all in my Data Layer (in one project), remember we have multiple projects (Multiple Tier), and i set one of the projects as the StartUp. So my solution was to uninstall Misoft.EntityFrameworkCore.SqlServer and Misoft.EntityFrameworkCore.Tools from the Data layer (that is the project where I have my DbContext) and install them (Misoft.EntityFrameworkCore.SqlServer and Misoft.EntityFrameworkCore.Tools) in the Dependencies of StartUp project.

HOW TO INSTALL Right click on the Dependencies in the StartUp project, select: Manage NuGet Packages.. Click install and search the above two packages.

Projects in the Application Image of how it should look after following the below steps

Install this Nuget Package --> Microsoft.EntityFrameworkCore.Design

And run migrations again

In my case I had multiple projects set to start up, once I set it to a single project the Add-Migration command worked:

And: