ASP.NET WebAPI 2: How to pass empty string as parameter in URI

Question

I have a function like this in my ProductsController:

public IHttpActionResult GetProduct(string id) { var product = products.FirstOrDefault((p) => p.Id == id); return Ok(product); }

When I send a GET request with this URL:

 api/products?id=

it treats id as null. How can I make it to treat it as an empty string?

Use optional parameter string id = "" then you can call GET api/products/ — Ric
– Ric, Commented Jan 6, 2016 at 10:05
@Ric What if i want GET api/products to return an error? Because I think it will be ambiguous — Tu Anh
– Tu Anh, Commented Jan 6, 2016 at 10:24
ambiguous in what sense? it depends how you have setup your routing etc and if you are uring resful api, — Ric
– Ric, Commented Jan 6, 2016 at 10:26

Steve Harris · Accepted Answer · 2016-01-06 10:22:34Z

This

public IHttpActionResult GetProduct(string id = "") { var product = products.FirstOrDefault((p) => p.Id == id); return Ok(product); }

or this:

public IHttpActionResult GetProduct(string id) { var product = products.FirstOrDefault((p) => p.Id == id ?? ""); return Ok(product); }

For me it just worked when adding a default value to the parameter in the method signature.

LMK · Accepted Answer · 2020-09-01 20:19:49Z

I have a situation where I need to distinguish between no parameter passed (in which case default of null is assigned), and empty string is explicitly passed. I have used the following solution (.Net Core 2.2):

[HttpGet()] public string GetMethod(string code = null) { if (Request.Query.ContainsKey(nameof(code)) && code == null) code = string.Empty; // .... }

Exactly what I needed. Looks like the behavior is different in .NET Framework and .NET Core. The former allows you to pass in an empty string.

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