Where to put code to run after startup is completed

Question

I have an aspnetcore app.

During startup, it does the usual startup actions.

After these are complete, I need to do some verification to ensure it was set up correctly. In particular, I need to call a stored procedure in the database using the default connection string. In other words, I need to create a class that uses dependency injection so that needs to be complete before it is called.

Just not sure where to put such code in StartUp.

Answer 1

Probably the best place is in Configure method after UseMvc() call. That is also the place where you usually apply migrations. You can add as many classes that DI knows as parameter.
For example:

public void Configure(IApplicationBuilder app) 

or

public void Configure(IApplicationBuilder app, AppUserManager userManager, IServiceProvider serviceProvider) 

or

public void Configure(IApplicationBuilder app, MyDbContext context) 

If you want to check this in background (only if you don't care about result - application should run also if verification fails), check my answer here.
Also this answer may help you.