Entity Framework Core Database First in Entity Framework Core with a Class Library and SQL Server


Example

Okay it took me about a day to figure it out so here I am posting the steps I followed to get my Database First working in a Class Project (.NET Core), with a .NET Core Web App.

Step 1 - Install .NET Core

Make Sure you are using .NET Core not DNX (Hint: You should be able to see the .NET Core option when creating a New Project) - If NOT Download from Here

If you have problems installing .NET Core (Error is something like Visual Studio 2015 Update 3 not installed correctly) - You can run the installing using the command: [DotNetCore.1.0.0-VS2015Tools.Preview2.exe SKIP_VSU_CHECK=1] -- Which will prevent the installation performing the Visual Studio Check Github Issue

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Step 2 - Create The Projects

Create a new ASP.NET Core Web Application --> Then Select Web Application in the next screen

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Add a Class Library (.NET Core) Project

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Step 3 - Installing EF Packages

Open your project.json file of Class Library, and paste the following, then Save the file:

{
  "version": "1.0.0-*",

  "dependencies": {
    "Microsoft.EntityFrameworkCore.SqlServer": "1.0.0",
    "Microsoft.EntityFrameworkCore.SqlServer.Design": "1.0.0",
    "Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final",
    "NETStandard.Library": "1.6.0"
  },
  "tools": {
    "Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final"
  },

  "frameworks": {
    "net46": {
    },
    "netcoreapp1.0": {
      "dependencies": {
        "Microsoft.NETCore.App": {
          "type": "platform",
          "version": "1.0.0-*"
        }
      }
    }
  }
}

This should restore the packages under References

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---------------- OR

You can install them using Nuget Package Manager by running the following commands in the Package Manager Console

Install-Package Microsoft.EntityFrameworkCore.SqlServer

Install-Package Microsoft.EntityFrameworkCore.Tools –Pre

Install-Package Microsoft.EntityFrameworkCore.SqlServer.Design

Note: Install one Package at a time - if you get an error after installing

Microsoft.EntityFrameworkCore.Tools

Then change the content of your project.json frameworks section to this:

  "frameworks": {
    "net46": {
    },
    "netcoreapp1.0": {
      "dependencies": {
        "Microsoft.NETCore.App": {
          "type": "platform",
          "version": "1.0.0-*"
        }
      }
    }
  }

Step 4 - Creating the Database Model

Now to generate the Database run the following command in the Package Manager Console (DON'T forget to Change the connection string to your Database)

Scaffold-DbContext "Server=. ; Database=DATABASE; user id= USER ; password = PASSWORD;" Microsoft.EntityFrameworkCore.SqlServer

This will give you the Error about Startup Project:

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For this you have to add the same references you added to Class Library to the .NET Web App

So open your project.json for the Web App,

Under dependencies, add:

"Microsoft.EntityFrameworkCore.SqlServer": "1.0.0",
"Microsoft.EntityFrameworkCore.SqlServer.Design": "1.0.0",
"Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final",

and under tools add:

"Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final",

After making the changes Save the file.

This is what my project.json looks like

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Then again run the command in Package Manager Console against the class library:

If you haven't already added the reference of your Class Library to the Web App, you will get this error:

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to solve this add reference of your class Library to your Web App:

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Finally

Run the Command again - in the Package Manager Console:

Scaffold-DbContext "Server=. ; Database=DATABASE; user id= USER ; password = PASSWORD;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models

This should create the Entities under Models Folder, in the class library

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Passing a Connection String

In my case here, we have a Multi Tenant Application, in which each client has their own Database, e.g. Client_1, Client_2, Client_3. So the connection string had to be dynamic.

So we added a connection string property to a constructor, and passed it to the Context in the OnConfiguring method

public partial class ClientContext
{
    private readonly string _connectionString;

    public ClientContext(string connectionString) : base()
    {
        _connectionString = connectionString;
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer(_connectionString);
    }
}

and used it like this:

    public void TestConnection()
    {
        var clientId = 1;

        var connectionString = string.Format("Server=192.168.0.211; Database=Client_{0}; user id= USER; password = PWD;", clientId);

        using (var clientContext = new ClientContext(connectionString))
        {
            var assets = clientContext.Users.Where(s => s.UserId == 1);
        }
    }