Upgrade from .NET 6 to .NET 8: Custom Context with Configuration - DB First

Question

I want to upgrade from .NET 6 to .NET 8. I have to use DB first approach. In .NET 6 I created a custom context to be able to pass a connectionString from the injected Configuration.

public partial class ScaffoldedCustomContext : ScaffoldedContext
{
    private IConfiguration _config;

    public ScaffoldedCustomContext(IConfiguration Configuration)
    {
        _config = Configuration;
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        if (!optionsBuilder.IsConfigured)
        {
            optionsBuilder.UseSqlServer(_config.GetValue<string>("connectionString"));
        }
    }
}

After "switching" to .NET 8 (package upgrades and changing my VS code launch.json) the DB scaffold creates the following context file:

public partial class ScaffoldedContext : DbContext
{
    public ScaffoldedContext(DbContextOptions<ScaffoldedContext> options)
        : base(options)
    {
    }
    ...
}

with .net6 I was also given an empty default constructor:

public ScaffoldedContext()
{
}

In some of my methods for example in "Main" I needed to create a context like this:

 var _context = new ScaffoldedCustomContext(Configuration);

But with .NET 8 I get the error message that the required parameter options is missing.

How can I deal with that? Do I need to modify ScaffoldedCustomContext or do I have to create an options object - if yes, how?

Thank you.

why don't you just resolve the ScaffoldedContext from IServiceProvider ? — J.Memisevic
– J.Memisevic, Commented Mar 21, 2024 at 10:29

Guru Stron · Accepted Answer · 2024-03-21 14:08:05Z

Arguably you don't need ScaffoldedCustomContext class at all. ScaffoldedContext is generated as partial so you should be able to just create a file named something like ScaffoldedContext.Custom and place it near the generated one (be sure to place them in the same namespace) and move all custom stuff there:

 public partial class ScaffoldedContext
 {
     private IConfiguration _config;

     public ScaffoldedContext(IConfiguration Configuration)
     {
         _config = Configuration;
     }

     protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
     {
         if (!optionsBuilder.IsConfigured)
         {
             optionsBuilder.UseSqlServer(_config.GetValue<string>("connectionString"));
         }
     }
 }

Without seeing your Main it is hard to tell what is the best course of action is but
- Depending on the setup you potentially can just resolve the ScaffoldedContext in the Main - see for example Cannot resolve scoped service from root provider in ASP.NET Core 6
- Similar to the previous - register context factory, resolve and use it to construct the context
- Construct the options so you don't need the custom constructor:
```
var options = new DbContextOptionsBuilder<ScaffoldedContext>()
    .UseSqlServer(Configuration.GetValue<string>("connectionString"))
    .Options;
var ctx = new ScaffoldedContext(options);
```

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