Receiving "null" instead of null

Question

I'm trying to pass a null argument to a web api controller but I'm getting "null" instead of null.

E.g : my route should be like this

[Route("api/student/GetStudent/{studentId}/{studentFname}/{studentLname}/")] public Student GetStudent(int studentId,string studentFname,string studentLname) { //Code }

Note that at least user should insert first name or last name and isn't required to have both

In the above code , both firstname and lastname are required but I don't want this. So I change my code to be like this

[Route("api/student/GetStudent/{studentId}/{studentFname?}/{studentLname?}/")] public Student GetStudent(int studentId,string studentFname,string studentLname) { //Code }

As I said that when I call this method and pass a null argument for student firstname . I am getting "null" and when it pass to the database stored procedure it will pass as a value.

Because having your url constructed as "/api/student/getStudent/123/null/null" will still evaluate to string values. How would it know that my surname is in fact not written as "Null"? Pass a model in, rather than values in segments and problem will be solved. — Adrian
– Adrian, Commented Oct 16, 2019 at 10:20
What does the URL look like? Did you actually pass the string null perhaps? In any case this code is wrong - GET is used to *request stuff, not send stuff to the server. Use POST instead. — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Oct 16, 2019 at 10:21
This is the opposite problem. I think the issue in this case isn't that the behavior is wrong, but that your expectation is wrong. If you literally put a "null" into the URL, then the model binder's response (giving you a "null" string) is the correct behavior. — Flater
– Flater, Commented Oct 16, 2019 at 10:22
pass a null argument for student firstname URLs are strings, they know nothing about nulls. If you call /api/student/GetStudent/1/null, you *have* specified a value for studentFname` whose contents are "null". An optional parameter is one that doesn't have to be passed at all - use api/student/GetStudent/1 — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Oct 16, 2019 at 10:22
By the way, if you always expect id why do you ask for first and last name? — tmaj
– tmaj, Commented Oct 16, 2019 at 10:28

tmaj · Accepted Answer · 2019-10-16 10:40:20Z

This is most likely because the method is called as

api/student/GetStudent/xxx/null/something

null in this case is provided and is in fact "null".

You may need to expose

api/student/GetStudentByLastName/{lname}
api/student/GetStudentByFirstName/{fname}
api/student/GetStudentById/{id}

Depending on your setup you may be able to do

api/student/GetStudent/IdHere?fname=xxx (lname will be null)
api/student/GetStudent/IdHere?lname=xxx (fname will be null)

(btw. I'm not sure why you pass the name parts, if id is required)

dilipkumar1007 · Accepted Answer · 2019-10-16 10:36:57Z

0

I suppose you should call your API with below format:

api/student/GetStudent/studentId=&studentFname=&studentLname=

answered Oct 16, 2019 at 10:36

dilipkumar1007

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1 Comment

John Not Travolta Over a year ago

I know this behavior but I want to pass them like this /something/something

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