如何在没有任何硬编码连接字符串的情况下在我的 DbContext 中设置 OnConfiguring 方法？

Question

I'm using multiple examples on how to set up my MySql service but in almost every one (including the Microsoft), they are using a hard coded connection string.

This is my startup:

    services.AddDbContext<DbContext>(options =>
    {
        options.UseMySql(configuration.GetConnectionString("DefaultConnection"),
        mysqlOptions =>
        {
            mysqlOptions.ServerVersion(new ServerVersion(new Version(8, 0, 18)));
        });
    });

And whenever I try to Update-Database I see an error telling me that there's no password setted

MySql.Data.MySqlClient.MySqlException (0x80004005): Access denied for user 'root'@'localhost' (using password: YES).

After looking around a bit I found an overrideable method called OnConfiguring , but I want to set the connection string in a dynamic way, cause If I change my environment, I want that string to change too.

This is where I found almost every example with hardcoded strings (ex. https://dev.mysql.com/doc/connector-net/en/connector-net-entityframework-core.html )

Answer 1

You need to init configuration if not configured.

This can be done by overriding the OnConfiguring method in DbContext .

This way you can have global application configuration that will be pulled when application is ran. And use local configuration when doing Db migration.

Try this

public class YourContext: DbContext
{

    protected override void OnConfiguring(DbContextOptionsBuilder options)
    {
        if (options.IsConfigured == false)
            options.UseMysql({YOUR_CONNECTION_STRING});
    }
}

Answer 2

in configuration file, you should have a ConnectionStrings that points to your database with other options.

"ConnectionStrings": {
   "DefaultConnection": "server=127.0.0.1;uid=root;pwd=12345;database=test"
},

When you use configuration.GetConnectionString, you are looking up a value from the configuration section.

Answer 3

Try this at startup.cs

public class Startup
{
    private readonly IConfiguration _config;

    public Startup(IConfiguration config) 
    {
        _config = config;
    }

    // This method gets called by the runtime. Use this method to add services to the 
    container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext<MainContext>(options => 
           options.UseOracle(_config["CONNECTION_STRING"]));
    }
 }

And do that at your Context ctor

public MainContext(DbContextOptions<MainContext> options) : base(options) { }

Answer 4

Based on the comment , I think you want to separate the EF Core related classes to a different assembly.

In the UseMySql there is an option to configure MigrationsAssembly . You can get more details here

Here is pseudo-code for SQL Server.

services.AddDbContext<EFCoreDemoContext>(options =>
{
    options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection"),
            assembly => assembly.MigrationsAssembly(typeof(EFCoreDemoContext).Assembly.FullName));
});

Answer 5

I am addressing this portion of your question:

"After looking around a bit I found an overrideable method called OnConfiguring, but I want to set the connection string in a dynamic way, cause If I change my environment, I want that string to change too."

In order to solve getting the connection string into the OnConfiguring method inside your DbContext class I simply passed IConfiguration into the DbContext constructor like this.

    private readonly IConfiguration _config;

    public CoreDbContext(IConfiguration config)
    {
        _config = config;
    }

    public CoreDbContext(DbContextOptions<CoreDbContext> options, 
                         IConfiguration config) : base(options)
    {
        _config = config;
    }

Then in the OnConfiguring method I pulled the connection string from that config object injected at construction. Like this:

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        if (!optionsBuilder.IsConfigured)
        {
            optionsBuilder.UseSqlServer(_config.GetConnectionString("YourKeyValueForConnStringInAppSettings.json"));
        }
    }

Finally here are details of my environment / Project:

• Windows 10 machine
• Visual Studio 2022 (Version 17.0.4)
• ASP.NET Core Web API
• .NET 6.0
• Configure for HTTPS
• Use controllers checked
• Enable OpenApi support
• Authentication type at time of writing is None