.net MVC Action with Optional Parameters

Question

I want that controller will accept /Details/1 and /User/xxx but not /User/

and i try it like below=>

    public ActionResult Details( Nullable<int> id, Nullable<string> name)
    {
        if (((id ?? 0) == 0) && name == null)
        {
            return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
        }

        Instructor instructor = db.Instructors.Where(x => x.InstructorId == id || x.faculty_name.Equals(name)).SingleOrDefault();

        if (instructor == null)
        {
            return HttpNotFound();
        }

        ViewBag.faculty_active = MyCustomFunctions.UserActivity();
        return View(instructor);
    }

i want that(mansion above) user can pass /Details/1 or /Details/xxx but not /Details/ thats why i add condition check=>

        if (((id ?? 0) == 0) && name == null)
        {
            return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
        }

but i wants to run the code the compiler gives me error something like=> i was thinking that was perfect but i dont know why a have done wrong = i tried=>

    public ActionResult Details( int? id, string? name)
    {
    }

that was also gives me the same error.i searched about this problem and i found=> ASP.NET MVC Overriding Index action with optional parameter

i am not understanding anything . thats why i reposed this kind of problems. this will be great full if anybody can help me?

string is already nullable. But you cannot have 2 nullable values as parameters and use routes (you will only be able to generate /Details?name=xxx - if you were to use /Details/xxx both parameters will be null and your code will always return BadRequest) — user3559349
– user3559349, Commented May 16, 2017 at 9:10
@StephenMuecke public ActionResult Details( int id = 0, string name = null) is return me a bad request....is there any way to solve this problem or i need to follow other structure — nayan chowdhury
– nayan chowdhury, Commented May 16, 2017 at 9:19
Just have one parameter (string) and then check if it can be parsed to int — user3559349
– user3559349, Commented May 16, 2017 at 9:21
@StephenMuecke i can understand can you just give me one little example? — nayan chowdhury
– nayan chowdhury, Commented May 16, 2017 at 9:23

user3559349 · Accepted Answer · 2017-05-16 09:43:33Z

string is already nullable so Nullable<string> and string? make no sense. However you cannot have 2 nullable parameters and achieve the routes you want. The routing engine has no way of knowing which of the parameters should be bound, and if you were to use ../Details/xxx both values would be null and you would always be returning HttpStatusCode.BadRequest.

You could achieve this using 2 separate methods (say DetailsByID and DetailsByName) and route definitions, but if you want a single method, then you can only have one parameter to account for all 3 routes. In the method you can then attempt to parse the value to int

public ActionResult Details(string id)
{
    if (id == null)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }
    int number;
    Instructor instructor;
    bool isInt = Int32.TryParse(id, out number);
    if (IsInt)
    {
        instructor = db.Instructors.Where(x => x.InstructorId == number).SingleOrDefault();
    }
    else
    {
        instructor = db.Instructors.Where(x => x.faculty_name.Equals(id)).SingleOrDefault();
    }
    if (instructor == null)
    {
        return HttpNotFound();
    }
    ViewBag.faculty_active = MyCustomFunctions.UserActivity();
    return View(instructor);
}

Mihai Alexandru-Ionut · Accepted Answer · 2017-05-16 09:48:13Z

2

Don't use Nullable<string> because you do not needed and makes no sense.

string already accepts null value and that means is already nullable.

Short example:

string myString=null;

edited May 16, 2017 at 9:48

answered May 16, 2017 at 8:59

Mihai Alexandru-Ionut

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Comments

Sameer549 · Accepted Answer · 2017-05-16 09:32:52Z

0

You need to add Nullable for Value Types, like int,demical,DateTime etc,.

String is a reference type so it allows null by default

answered May 16, 2017 at 9:32

Sameer549

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