Getting DbContext when resolving a singleton

Question

Within ConfigureServices I have

services.AddDbContext(options => options.UseSqlServer(Configuration.GetConnectionString(\"De         


        

Answer 1

AddDbContext defaults to using a scoped lifestyle:

Scoped lifetime services (AddScoped) are created once per client request (connection).

The reason an error is being thrown is that you're attempting to obtain an instance of MyContext from outside of a request. As the error message suggests, it is not possible to obtain a scoped service from the root IServiceProvider.

For your purposes, you can create a scope explicitly and use that for your dependency resolution, like so:

services.AddSingleton<IMyModel>(sp =>
{
    using (var scope = sp.CreateScope())
    {
        var dbContext = scope.ServiceProvider.GetService<MyContext>();
        var lastItem = dbContext.Items.LastOrDefault();
        return new MyModel(lastItem);
    }
});    

This code above creates a scoped IServiceProvider that can be used for obtaining scoped services.