How to send empty route parameter to a web API?

Question

I am calling a web api using this code

public class SearchController : ApiController
{
    [Route("api/SearchController/{paramOne}/{paramTwo}")]
    public string Get(string paramOne, string paramTwo)
    {
        return "The [Route] with multiple params worked.\nP1 : " + paramOne + "    P2 : " + paramTwo;
    }
}

It works fine.

if I call https://localhost:44319/api/SearchSelectController/Mike/Tom

I get this

<string xmlns="http://schemas.microsoft.com/2003/10/Serialization/">
<link type="text/css" rel="stylesheet" id="dark-mode-custom-link"/>
<link type="text/css" rel="stylesheet" id="dark-mode-general-link"/>
<style lang="en" type="text/css" id="dark-mode-custom-style"/>
<style lang="en" type="text/css" id="dark-mode-native-style"/>
The [Route] with multiple params worked. P1 : Mike P2 : Tom
</string>

but if I am sending empty string for the first or 2nd parameter

https://localhost:44319/api/SearchSelectController//Tom

I get this error

<Error>
<link type="text/css" rel="stylesheet" id="dark-mode-custom-link"/>
<link type="text/css" rel="stylesheet" id="dark-mode-general-link"/>
<style lang="en" type="text/css" id="dark-mode-custom-style"/>
<style lang="en" type="text/css" id="dark-mode-native-style"/>
<Message>No HTTP resource was found that matches the request URI 'https://localhost:44319/api/SearchSelectController/Tom'.</Message>
<MessageDetail>No type was found that matches the controller named 'SearchSelectController'.</MessageDetail>
</Error>

So I wonder how can I send empty string as parameter for a web API?

Answer 1

In this case only one solution exists. Use query parameter like below:

public class SearchController : ApiController
{
    [Route("api/SearchController")]
    public string Get([FromQuery] ModelWithTwoParam model)
    {
        return "The [Route] with multiple params worked.\nP1 : " + model.paramOne + "    P2 : " + model.paramTwo;
    }
}

see documents:

[FromQuery]

Answer 2

It is not possible to send empty route parameters, because they break the URL-schema.
To solve your problem you can send them as GET-Parameters. So your method in the Controller looks like:

[Route("api/SearchController")]
public string Get(string paramOne = null, string paramTwo= null)
  {
    return "The [Route] with multiple params worked.\nP1 : " + paramOne + "    P2 : " + paramTwo;
  }

The URLs look like this:

https://localhost:44319/api/SearchSelectController?paramOne=Mike&paramTwo=Tom
https://localhost:44319/api/SearchSelectController?paramTwo=Tom
https://localhost:44319/api/SearchSelectController?paramOne=Mike

Answer 3

If each input parameter may be null or any combination of these, tell the action method that each of these may be null. The following code also supports null values.

[Route("api/SearchController/{paramOne?}/{paramTwo?}")]
public string Get(string paramOne = null, string paramTwo = null)
{
    return "The [Route] with multiple params worked.\nP1 : " + paramOne + "    P2 : " + paramTwo;
}

Or another method

set the WebApiConfig.cs file as follows. If you do not have this file, create it in the App_Start folder.

public static class WebApiConfig
{
     public static void Register(HttpConfiguration config)
     {
       config.MapHttpAttributeRoutes();

       config.Routes.MapHttpRoute(
            name: "myroute",
            routeTemplate: "api/SearchController/{paramOne}/{paramTwo}",
            defaults: new { controller = "Search", action = "Get", paramOne = RouteParameter.Optional, paramTwo = RouteParameter.Optional }
        );

         config.Routes.MapHttpRoute(
              name: "DefaultApi",
              routeTemplate: "api/{controller}/{action}/{id}",
              defaults: new { id = RouteParameter.Optional}
        );
    }
}

and register above class in global.cs

protected void Application_Start()
{   /................
    GlobalConfiguration.Configure(WebApiConfig.Register);
    /................
}

Finally the api method

public string Get(string paramOne = null, string paramTwo = null)
{
    return "The [Route] with multiple params worked.\nP1 : " + paramOne + "    P2 : " + paramTwo;
}