Web API optional parameters

Question

I have a controller with the following signature:

[Route("products/filter/{apc=apc}/{xpc=xpc}/{sku=sku}")]
public IHttpActionResult Get(string apc, string xpc, int? sku)
{ ... }

I call this method with following URIs:

~/api/products/filter?apc=AA&xpc=BB
~/api/products/filter?sku=7199123

The first URI works without issue. The second one has a strange side effect. Even though the default values for apc and xpc should be null when not provided, the parameters are actually their names. I can overcome this by adding the additional logic:

apc = (apc == "apc") ? null : apc;
xpc = (xpc == "xpc") ? null : xpc;

This seems like a hack, and would be problematic if value passed was ever equal to the parameter name.

Is there a way to define the Route without this side effect?

You provided default values in your route template. Why would you expect them to be null? — Kenneth K.
I thought {sku=sku} mapped the parameter in the query string to the method parameter. — Josh
You should review the documentation for attribute routing. It shows how to make parameters optional. — Kenneth K.

Josh Josh · Accepted Answer · 2016-07-07T15:51:29

I figured it out. I was using a bad example I found in the past of how to map query string to the method parameters.

In case anyone else needs it, in order to have optional parameters in a query string such as:

~/api/products/filter?apc=AA&xpc=BB
~/api/products/filter?sku=7199123

you would use:

[Route("products/filter/{apc?}/{xpc?}/{sku?}")]
public IHttpActionResult Get(string apc = null, string xpc = null, int? sku = null)
{ ... }

It seems odd to have to define default values for the method parameters when these types already have a default.

Web API optional parameters

4 Answers