Passing data to .Net MVC controller method as parameters

Question

I just wonder when we pass data to controller method as parameters, why we need to use exactly the same name, any underlying reason?

For example, the following ajax call:

$.ajax({
            // Get Faculty PartialView
            url: "/Home/FacultiesToPVDemo",
            type: 'Get',
            data: { courseName: selectedCourseName },
            success: function (data) {
                $("#facultyDetailTable").empty().append(data);
            },
            error: function () {
                alert("something seems wrong");
            }
        });

will invoke the following method in the controller:

 public ActionResult FacultiesToPVDemo(string courseName)
    {
        IEnumerable<Course> allCourses = _repository.GetCourses();
        var selectedCourseId = (from c in allCourses where c.CourseName == courseName select c.CourseId).FirstOrDefault();

        IEnumerable<Faculty> allFaculties = _repository.GetFaculties();
        var facultiesForCourse = allFaculties.Where(f => f.AllotedCourses.Any(c => c.CourseId == selectedCourseId)).ToList();

        return PartialView("FacultyPV", facultiesForCourse);
    }

In the ajax if I use a different data property name other than "courseName", it wouldn't work, even if there is only one parameter to match. why is that?

it's the model binding that looks to match the parameter names...you could still get the value from the Request — dotjoe, Aug 04 '15 at 14:29
alternatively, you could write a custom ModelBinder that evaluates the Request object to make the call work :) — Icepickle, Aug 04 '15 at 14:31
@Icepickle: Oh don't suggest *that*. I know you're trying to be funny, but someone's liable to go off and do something that silly. If you think a custom model binder is the answer, most likely you're asking the wrong question. — Chris Pratt, Aug 04 '15 at 14:33
@dotjoe how the parameter is related to model? I think it just serves as a "parameter" for other data to fill in — strisunshine, Aug 04 '15 at 14:33

score 1 · Answer 1 · answered Aug 04 '15 at 14:33

1

In exactly the same way that you cannot declare a method as:

public void Test(string test = null)

.. and expect this to work:

obj.Test(notTest: null)

If you're not passing your data over with the correct name, it won't bind. Just think of it in the same way, you are calling a method, albeit abstracted by ASP.NET / IIS through a routed HTTP request.

This allows you to have actions that have the same name, but different parameters should you need to accept them and is a benefit rather than a burden.

We may be able to help explain further or suggest alternatives if you give us a scenario where you would like things to be named differently. Things such as custom model binders, action filters (or anything overly complex) or accessing the form values directly (as a keyed array) are always an option depending on your actual requirements.

answered Aug 04 '15 at 14:33

Rudi Visser

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Ok so what I get is the naming matching is required for the binding to work . It was just defined so, but to me "courseName" is just a parameter in that function to find data in models – strisunshine Aug 04 '15 at 14:52
Well, in a logical mind - `courseName` is a course name. If you want to accept something else, add an overload (with a default value, `null`?) or a different method entirely that deals with your separate parameter. The appropriate method will be called depending on what parameters you actually pass over. – Rudi Visser Aug 04 '15 at 14:58
Okay, I mean sometimes as humans we may spell a different way, like "coursename" then it wouldn't match-) – strisunshine Aug 04 '15 at 15:03
It's static and defined in your javascript code, I don't see why this matters. – Rudi Visser Aug 04 '15 at 15:05
Never mind, thanks for your help :) – strisunshine Aug 04 '15 at 15:07

score 1 · Answer 2 · answered Aug 04 '15 at 14:38

1

The MVC ModelBinder needs the names to match in order for it to know how to relate the incoming request data to the correct parameters.

6 Tips for ASP.NET MVC Model Binding

answered Aug 04 '15 at 14:38

Oliver

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Thanks. What I get is that is just how it works. If there are more than one parameter and we use different names, the ModelBinder would be rather confused, right -: – strisunshine Aug 04 '15 at 14:56

Passing data to .Net MVC controller method as parameters

2 Answers2