C# Controller behavior changes based on variable name-CodePudding

I don't know enough about C#, .NET, or the MVC pattern to know exactly what is relevant to include here, but I'm pulling my hair out with a very simple change I'm working on.

I have a controller with a Search action (method?) that looks like:

public string Search(int id)
{
    return $"The id was {id}";
}

and when I hit the route I get the expected response, e.g.

$ curl https://localhost:7180/Players/Search/1
The id was 1

but when I change the variable name from id to anything else, the behavior changes and the value goes to 0 for some reason.

public string Search(int thing)
{
    return $"The thing was {thing}";
}

$ curl https://localhost:7180/Players/Search/1
The thing was 0

I thought maybe it had to do with the Model itself, because the model code at least has an Id attribute

    public class Player
    {
        public int Id { get; set; }
        public string? Name { get; set; }
    }

but renaming that variable to name (which seems analogous) also doesn't help.

So what concept am I missing here? Why can't I just rename that variable to whatever I want? Thanks in advance!

(I don't know how better to communicate all the different aspects of the code, so here is a link to the line in question, inside the project)

CodePudding user response：

By default MVC registers (see either Program or Startup) next default route, so it can bind id parameter of method as positional part of path:

app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}");

You can change the parameter name for example using attribute routing:

[Route("[controller]/search/{thing}")] 
public string Search(int thing)
{
    return $"The thing was {thing}";
}

Or using HTTP verb templates:

[HttpGet("[controller]/search/{thing}")] 
public string Search(int thing)
{
    return $"The thing was {thing}";
}

Check the linked docs for other options/details.

CodePudding user response：

You can decorate the method and define the parameter.

    // GET api/values/5
    [HttpGet("{id}")]
    public virtual async Task<ActionResult<IEntity>> Get(string id)
    {
        var entity = await Repository.GetEntity(x => x.Id == id);
        if (entity == null) return NotFound();

        return Ok(entity);
    }

CodePudding user response：

I believe this has to do with the way you've defined your route in Program.cs:

app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}");

You'll want to add a new definition like this:

app.MapControllerRoute(
    name: "default",
    pattern: "Players/Search/{thing?}");

alternatively, you could use attribute-based route definitions to move the route pattern definition closer to the actual code. See the MSFT docs for details. Basically, add app.MapControllers(); to Program.cs, then for your individual routes, do something like this:

[Route("Player/Search/{thing}")
public string Search(int thing)
{
    return $"The thing was {thing}";
}