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?

Solution 1

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);
}

Solution 2

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;

   // ....
}
    

Comments

[Jehof]

GetProduct(string id = string.Empty)

[Ric]

Use optional parameter string id = "" then you can call GET api/products/

[ssilas777]

msdn.microsoft.com/en-us/library/…

[Tu Anh]

@Ric What if i want GET api/products to return an error? Because I think it will be ambiguous

[Ric]

ambiguous in what sense? it depends how you have setup your routing etc and if you are uring resful api,

[Tu Anh]

@Ric I afraid that people may think GET api/products will return all products.

[Ric]

I would also think the same!

[rohitwtbs]

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

[Joel Christophel]

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.