ASP.NET Core MVC generates an exception error when referencing a database connection

Question

I have the following code in a controller which, when executed, displays the view to the user in the browser:

public class PlayerController : Controller

{
    private readonly IPlayerRepository repo;
    public IActionResult Index()
    {
        return View();
    }
    [HttpPost]
    public ActionResult Index(Player person)
    {
        var lastName = person.LastName;
        var firstName = person.FirstName;
        var callPlayer = new PlayerInit();
        var returnPlayer = callPlayer.SetUpPlayer(lastName, firstName);

        return View();
    }
}

When I add this code, an exception is thrown:

    public PlayerController(IPlayerRepository repo)
    {
        this.repo = repo;
    }

This is the exception that gets thrown:

I have similar code in a different controller and I am able to run that controller to access a mySql database via dapper and display the results to the view. Im not sure why the code in this particular controller is having an issue.

Thank you!

The error is clear and has nothing to do with databases. Have you registered any IPlayerRepository-derived class? What does your Startup.cs look like? — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Nov 26, 2021 at 16:23

Wai Ha Lee · Accepted Answer · 2021-11-27 09:30:50Z

2

Usually this error is caused because in the Startup.cs file the ConfigureServices method does not contain the code that will inject the dependency to the container.

public void ConfigureServices(IServiceCollection services)
{
    // OMITTED

    services.AddScoped<IPlayerRepository, PlayerRepository>();

    // OMITTED
}

You can also take a look to the documentation on how all the dependency injection works in dotnet starting here.

edited Nov 27, 2021 at 9:30

Wai Ha Lee

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answered Nov 26, 2021 at 16:41

Juan Carlos Jimenez

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