How can I implement DbContext Connection String in .NET Core?

Question

My situation is quite similar to this link or at least my code is similar and I am trying to find a way to apply this same method in .NET Core syntax.

Pass connection string to code-first DbContext

My specific code is as follows:

public partial class CompanyFormsContext : DbContext
{
    public CompanyFormsContext()
        : base("name=CompanyFormsContext")
    {
    }

    public CompanyFormsContext(string connName)
        : base("name=" + connName)
    {
    }
    ...
}

I get an error saying:

Error CS1503 Argument 1: cannot convert from 'string' to 'Microsoft.EntityFrameworkCore.DbContextOptions' CompanyForms..NETCoreApp,Version=v1.0

when I go over the parenthesis in base("name=CompanyFormsContext") or base("name=" = connName).

What is the correct way of implementing this functionality in .NET Core?

Edit:

I wanted to share that I have the following information for database connection in my appsettings.json file: (However, I do not have settings in the startup.cs)

  "Data": {
    "CompanyFormsContext": {
      "ConnectionString": "Server=(localdb)\\projectsv13;Database=companyforms;Trusted_Connection=True;"
    },
    "CompanyFormsContextQA": {
      "ConnectionString": "Server=(localdb)\\projectsv13;Database=companyforms;Trusted_Connection=True;"
    }
  }

and I have found the following link Adding DbContextOptions in Startup.cs not registering data store in the website and I am wondering if a simple protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) will be enough to fix my connection or not?

From the link:

services.AddEntityFramework(Configuration)
    .AddSqlServer()
    .AddDbContext<MyDbContext>(
        options =>
        options.UseSqlServer(Configuration.Get("Data:CompanyFormsContext:ConnectionString"))
    );

Do I need this kind of a service in my Startup.cs?

Solution 1

Another option would be to call the base constructor that takes a DbContextOptions:

public BooksContext(string connectionString) : base(GetOptions(connectionString))
{
}

private static DbContextOptions GetOptions(string connectionString)
{
    return SqlServerDbContextOptionsExtensions.UseSqlServer(new DbContextOptionsBuilder(), connectionString).Options;
}

Solution 2

Generally you are going to want to read it from config at start-up, and then use the connection string to configure an Entity Framework DbContext service for your process.

1) Add a line to your appsettings.json:

"DbConnectionString": "Server=s;Database=db;Trusted_Connection=True;",

2) Read the line in you Startup.cs class (after the Startup method is called to build the Configuration - so usually in the ConfigureServices method) like this:

var connection = Configuration["DbConnectionString"];

3) If using Entity Framework add a database context service (MyDbContext is the context class generated by EF). You also want to tell the built-in dependency injection how to instantiate your database context:

services.AddDbContext<MyDbContext>(options => options.UseSqlServer(connection));
services.AddScoped<IMyDbContext, MyDbContext>();

Where IMyDbContext is (at it's simplist) just an interface you've extracted from your MyDbContext

4) Now you can define your controller to take a MyDbContext and the DI will take care of building it and passing it in when the controller is invoked:

public MyController(IMyDbContext context)
{
    _context = context  // store for later use
}

Solution 3

IMO best practice:

add to your configuration.json:

     "ConnectionStrings": {
    "BooksContext": "Server=MyServer;Database=MyDb;Trusted_Connection=True;"
  }

and to initialize section:

services.AddDbContext<BooksContext>(options => options.UseSqlServer(configuration.GetConnectionString(nameof(BooksContext))));

Solution 4

An easy way is, just to use an optionbuilder to get the Context:

    public static MyDbContext GetMyDbContext(string databaseName)
    {
        var optionsBuilder = new DbContextOptionsBuilder<MyDbContext>();

        optionsBuilder.UseSqlServer($@"Data Source=.\SqlExpress;Initial Catalog={databaseName};Integrated Security=True");

        return new MyDbContext(optionsBuilder.Options);

    }

Solution 5

Startup.cs for static connection

services.AddScoped<MyContext>(_ => new MyContext(Configuration.GetConnectionString("myDB")));

Table1Repository.cs for dynamic connection

using (var _context = new MyContext(@"server=....){
context.Table1....
}

MyContext.cs

public MyContext(string connectionString) : base(GetOptions(connectionString))
{
}

private static DbContextOptions GetOptions(string connectionString)
{
    return SqlServerDbContextOptionsExtensions.UseSqlServer(new DbContextOptionsBuilder(), connectionString).Options;
}

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Comments

[aherrick]

had to change this to base but great solution!

[Terai]

And how can i use this for oracle database ?, there is no UseOracle or somthing like that..

[Ricardo Peres]

Microsoft does not provide one for Oracle, you need to use a third-party. Depending on it, the extension method may be different. Please see docs.microsoft.com/en-us/ef/core/providers.

[Tobias J]

If you need to get a strongly-typed DbContextOptions<TContext>, you need to use new DbContextOptionsBuilder<BooksContext>.

[Vamos]

It's work. This answer helps me a lot. Thanks.