Develop Reference

ASP.NET Web API - The requested resource does not support http method 'GET'

I am make POST call into my Web API using Postman. I get the error: "The requested resource does not support http method 'GET'."
I am not making a GET call. If I do call one of my GET methods, it works fine and returns the expected result.
My controller class:
[RoutePrefix("api/login")]
public class LoginController : ApiController
{
ModelContext db = new ModelContext();
[HttpPost]
[Route("validate")]
public HttpResponseMessage Validate([FromBody] LoginViewModel login)
{
try
{
var message = Request.CreateResponse(HttpStatusCode.OK);
return message;
}
catch (Exception ex)
{
var message = Request.CreateErrorResponse(HttpStatusCode.BadRequest, ex.Message);
return message;
}
}
}
I have the Web API running locally and call with this URL:
http://localhost:44303/api/login/validate
This url returns:
<Error>
<Message>
The requested resource does not support http method 'GET'.
</Message>
</Error>
My routing in WebApiConfig.cs
config.MapHttpAttributeRoutes();
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
While this controller message returns HttpResponseMessage, I have tested by changing the response to "string" and just returning a string value, but I get the same error.
I have read through so many SO posts but none appear to fix my issue. I am at a total loss to explain this behavior. I appreciate any ideas.
EDIT
I have tested GETs in other controllers and they are returning data as expected.
EDIT FOR CONTEXT 6/3/2020
This method in the default ValuesController works:
[Route("api/values")]
public IEnumerable<string> Get()
{
return new string[] { "value1", "value2" };
}
These 2 methods in the SAME controller do not work:
// GET api/values/5
public string Get(int id)
{
return "value";
}
// POST api/values
public void Post([FromBody]string value)
{
}
EDIT #2 6/3/2020
Now all of my api methods are working for the default ValuesController. I do not know why.
My custom POST methods in other controllers such as the Post method above are still not working. Here is my current WebApiConfig.cs:
public static void Register(HttpConfiguration config)
{
// Web API configuration and services
// Web API routes
config.MapHttpAttributeRoutes();
config.Routes.MapHttpRoute(
name: "Api_Get",
routeTemplate: "api/{controller}/{action}/{id}",
defaults: new { id = RouteParameter.Optional, action = "Get" },
constraints: new { httpMethod = new HttpMethodConstraint(HttpMethod.Get) }
);
config.Routes.MapHttpRoute(
name: "Api_Post",
routeTemplate: "api/{controller}/{action}/{id}",
defaults: new { id = RouteParameter.Optional, action = "Post" },
constraints: new { httpMethod = new HttpMethodConstraint(HttpMethod.Post) }
);
}
I do not have any middleware or special routing that I know of. Any exception handling would be simple try-catch.
I am trying to use attribute routing vs convention but that seems to be an issue.

You don't need to create a route table by HttpMethods because you have [HttpPost] attribute.
Replace all config.Routes.MapHttpRoute by
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
It's preferable to use Attribute Routing for Web API project. It will reduce the chances of errors because in RouteConfig class there can be any mistake while creating a new custom route. Also, you don’t have to take care of the routing flow i.e, from most specific to most general. All here is the attribute you use the action method.

Swagger-Net Shows controller name instead of endpoint method

I've been trying to figure out why Swagger-Net does not show the endpoint methods in a controller.
The C# project is using a Web API template based on .Net framework 4.6.1.
I get the same result when I use SwashBuckler, so it's not Swagger-Net that's the issue, but something that is not configured or missing.
The SwaggerConfig looks like this
public class SwaggerConfig
{
/// <summary>
///
/// </summary>
public static void Register()
{
var thisAssembly = typeof(SwaggerConfig).Assembly;
GlobalConfiguration.Configuration
.EnableSwagger(c =>
{
c.SingleApiVersion("v1", nameof(ConsentResponseApp));
c.AccessControlAllowOrigin("*");
c.IncludeAllXmlComments(thisAssembly, AppDomain.CurrentDomain.BaseDirectory);
})
.EnableSwaggerUi(c =>
{
c.UImaxDisplayedTags(100);
c.UIfilter("''");
});
}
}
I'm at a dead end at the moment since I have no idea why Swagger cannot read the methods action names.
The answer:
The WebApiConfig route is not by default configured to route with action
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
it has to be changed to
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "{controller}/{action}/{id}",
defaults: new { id = RouteParameter.Optional }
);

Building on Leon's comment. You need to specify a Route as Leon showed above.
I'm not sure [ActionName()] is what you need at all since it will allow your API's consumer to specify the URI with characters .NET may not allow or using a different signature than your actual controller method.
See this post for the reason behind [ActionName()].

You need a route, not an actionname
[Route("SaveConsent")]
Besides that, it is advisable to add expected responses like so:
[SwaggerResponse(HttpStatusCode.OK, "OK", typeof(User))] [SwaggerResponse(HttpStatusCode.BadRequest, "Error", typeof(string))] [SwaggerResponse(HttpStatusCode.NotFound, "Notfound", typeof(string))]
[Route("SaveConsent")]
[HttpPost]

Web API: Multiple actions were found that match the request [duplicate]

I keep getting this error when I try to have 2 "Get" methods
Multiple actions were found that match the request: webapi
I been looking around at the other similar questions about this on stack but I don't get it.
I have 2 different names and using the "HttpGet" attribute
[HttpGet]
public HttpResponseMessage Summary(MyVm vm)
{
return null;
}
[HttpGet]
public HttpResponseMessage FullDetails()
{
return null;
}

Your route map is probably something like this in WebApiConfig.cs:
routes.MapHttpRoute(
name: "API Default",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional });
But in order to have multiple actions with the same http method you need to provide webapi with more information via the route like so:
routes.MapHttpRoute(
name: "API Default",
routeTemplate: "api/{controller}/{action}/{id}",
defaults: new { id = RouteParameter.Optional });
Notice that the routeTemplate now includes an action. Lots more info here: http://www.asp.net/web-api/overview/web-api-routing-and-actions/routing-in-aspnet-web-api
Update:
Alright, now that I think I understand what you are after here is another take at this:
Perhaps you don't need the action url parameter and should describe the contents that you are after in another way. Since you are saying that the methods are returning data from the same entity then just let the parameters do the describing for you.
For example your two methods could be turned into:
public HttpResponseMessage Get()
{
return null;
}
public HttpResponseMessage Get(MyVm vm)
{
return null;
}
What kind of data are you passing in the MyVm object? If you are able to just pass variables through the URI, I would suggest going that route. Otherwise, you'll need to send the object in the body of the request and that isn't very HTTP of you when doing a GET (it works though, just use [FromBody] infront of MyVm).
Hopefully this illustrates that you can have multiple GET methods in a single controller without using the action name or even the [HttpGet] attribute.

Update as of Web API 2.
With this API config in your WebApiConfig.cs file:
public static void Register(HttpConfiguration config)
{
//// Web API routes
config.MapHttpAttributeRoutes(); //Don't miss this
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = System.Web.Http.RouteParameter.Optional }
);
}
You can route our controller like this:
[Route("api/ControllerName/Summary")]
[HttpGet]
public HttpResponseMessage Summary(MyVm vm)
{
return null;
}
[Route("api/ControllerName/FullDetails")]
[HttpGet]
public HttpResponseMessage FullDetails()
{
return null;
}
Where ControllerName is the name of your controller (without "controller"). This will allow you to get each action with the route detailed above.
For further reading: http://www.asp.net/web-api/overview/web-api-routing-and-actions/attribute-routing-in-web-api-2

In Web API (by default) methods are chosen based on a combination of HTTP method and route values.
MyVm looks like a complex object, read by formatter from the body so you have two identical methods in terms of route data (since neither of them has any parameters from the route) - which makes it impossible for the dispatcher (IHttpActionSelector) to match the appropriate one.
You need to differ them by either querystring or route parameter to resolve ambiguity.

After a lot of searching the web and trying to find the most suitable form for routing map
if have found the following
config.Routes.MapHttpRoute("DefaultApiWithId", "Api/{controller}/{id}", new { id =RouteParameter.Optional }, new { id = #"\d+" });
config.Routes.MapHttpRoute("DefaultApiWithAction", "Api/{controller}/{action}");
These mapping applying to both action name mapping and basic http convention (GET,POST,PUT,DELETE)

This is the answer for everyone who knows everything is correct and has checked 50 times.....
Make sure you are not repeatedly looking at RouteConfig.cs.
The file you want to edit is named WebApiConfig.cs
Also, it should probably look exactly like this:
using System.Web.Http;
namespace My.Epic.Website
{
public static class WebApiConfig
{
public static void Register(HttpConfiguration config)
{
config.MapHttpAttributeRoutes();
// api/Country/WithStates
config.Routes.MapHttpRoute(
name: "ControllerAndActionOnly",
routeTemplate: "api/{controller}/{action}",
defaults: new { },
constraints: new { action = #"^[a-zA-Z]+([\s][a-zA-Z]+)*$" });
config.Routes.MapHttpRoute(
name: "DefaultActionApi",
routeTemplate: "api/{controller}/{action}/{id}",
defaults: new { id = RouteParameter.Optional }
);
}
}
}
I could have saved myself about 3 hours.

It might be possible that your webmethods are being resolved to the same url. Have a look at the following link :-
http://www.asp.net/web-api/overview/web-api-routing-and-actions/routing-in-aspnet-web-api
So, you might need to add your methodname to your routing table.

Without using actions the options would be:
move one of the methods to a different controller, so that they don't clash.
use just one method that takes the param, and if it's null call the other method from your code.

This solution worked for me.
Please place Route2 first in WebApiConfig. Also Add HttpGet and HttpPost before each method and include controller name and method name in the url.
WebApiConfig =>
config.Routes.MapHttpRoute(
name: "MapByAction",
routeTemplate: "api/{controller}/{action}/{id}", defaults: new { id = RouteParameter.Optional });
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional });
Controller =>
public class ValuesController : ApiController
{
[HttpPost]
public string GetCustomer([FromBody] RequestModel req)
{
return "Customer";
}
[HttpPost]
public string GetCustomerList([FromBody] RequestModel req)
{
return "Customer List";
}
}
Url =>
http://localhost:7050/api/Values/GetCustomer
http://localhost:7050/api/Values/GetCustomerList

I found that that when I have two Get methods, one parameterless and one with a complex type as a parameter that I got the same error. I solved this by adding a dummy parameter of type int, named Id, as my first parameter, followed by my complex type parameter. I then added the complex type parameter to the route template. The following worked for me.
First get:
public IEnumerable<SearchItem> Get()
{
...
}
Second get:
public IEnumerable<SearchItem> Get(int id, [FromUri] List<string> layers)
{
...
}
WebApiConfig:
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}/{layers}",
defaults: new { id = RouteParameter.Optional, layers RouteParameter.Optional }
);

It is possible due to using MVC controller instead of Web API controller.
Check the namespace in Web API controller it should be as following
using System.Net;
using System.Net.Http;
using System.Web.Http;
If the namespace are as following then it is give above error in web api controller method calling
using System.Web;
using System.Web.Mvc;

Please check you have two methods which has the different name and same parameters.
If so please delete any of the method and try.

I've stumbled upon this problem while trying to augment my WebAPI controllers with extra actions.
Assume you would have
public IEnumerable<string> Get()
{
return this.Repository.GetAll();
}
[HttpGet]
public void ReSeed()
{
// Your custom action here
}
There are now two methods that satisfy the request for /api/controller which triggers the problem described by TS.
I didn't want to add "dummy" parameters to my additional actions so I looked into default actions and came up with:
[ActionName("builtin")]
public IEnumerable<string> Get()
{
return this.Repository.GetAll();
}
for the first method in combination with the "dual" route binding:
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { action = "builtin", id = RouteParameter.Optional },
constraints: new { id = #"\d+" });
config.Routes.MapHttpRoute(
name: "CustomActionApi",
routeTemplate: "api/{controller}/{action}");
Note that even though there is no "action" parameter in the first route template apparently you can still configure a default action allowing us to separate the routing of the "normal" WebAPI calls and the calls to the extra action.

In my Case Everything was right
1) Web Config was configured properly
2) Route prefix and Route attributes were proper
Still i was getting the error. In my Case "Route" attribute (by pressing F12) was point to System.Web.MVc but not System.Web.Http which caused the issue.

You can add [Route("api/[controller]/[action]")] to your controller class.
[Route("api/[controller]/[action]")]
[ApiController]
public class MySuperController : ControllerBase
{
...
}

I know it is an old question, but sometimes, when you use service resources like from AngularJS to connect to WebAPI, make sure you are using the correct route, other wise this error happens.

Make sure you do NOT decorate your Controller methods for the default GET|PUT|POST|DELETE actions with [HttpPost/Put/Get/Delete] attribute. I had added this attibute to my vanilla Post controller action and it caused a 404.
Hope this helps someone as it can be very frustrating and bring progress to a halt.

For example => TestController
[HttpGet]
public string TestMethod(int arg0)
{
return "";
}
[HttpGet]
public string TestMethod2(string arg0)
{
return "";
}
[HttpGet]
public string TestMethod3(int arg0,string arg1)
{
return "";
}
If you can only change WebApiConfig.cs file.
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{action}/",
defaults: null
);
Thats it :)
And Result :

Have you tried like:
[HttpGet("Summary")]
public HttpResponseMessage Summary(MyVm vm)
{
return null;
}
[HttpGet("FullDetails")]
public HttpResponseMessage FullDetails()
{
return null;
}

Why do my WebAPI RESTful routes throw 404 errors?

On a side-project I am working on, I am creating a RESTful API using WebAPI 2.2. The thing I'm working on is a means of accessing settings for a game. An example of the kind of routes I am trying to accomplish are as follows:
http://x/api/GameSettings/ <-- Returns all settings
http://x/api/GameSettings/audio <-- Returns the 'audio' category
http://x/api/GameSettings/audio/volume <-- Returns the key 'volume' in category audio
Note: the examples are all Get requests.
I've implemented the following controller...
public class GameSettingsController : ApiController
{
// GET /api/GameSettings
public HttpResponseMessage Get()
{
// Magic
return Request.CreateResponse(HttpStatusCode.OK, model);
}
public HttpResponseMessage Get(string category)
{
// Similar.
}
public HttpResponseMessage Get(string category, string key)
{
// Slightly different, but still similar.
}
}
I bound up the following MVC routes:
// Only necessary for the main view...
routes.MapRoute(
name: "Default",
url: "{controller}/{action}",
defaults: new { controller = "Home", action = "Index" }
);
And, I bound up the following WebAPI routes:
config.MapHttpAttributeRoutes();
config.Routes.MapHttpRoute(
name: "ApiGeneralCommand",
routeTemplate: "api/{controller}",
defaults: new { controller = "GameSettings" }
);
config.Routes.MapHttpRoute(
name: "ApiCategoryCommands",
routeTemplate: "api/{controller}/{category})",
defaults: new { controller = "GameSettings" }
);
config.Routes.MapHttpRoute(
name: "ApiKeyCommands",
routeTemplate: "api/{controller}/{category}/{key}",
defaults: new { controller = "GameSettings", category = "master" },
constraints: new { key = "[a-z0-9.-]" }
);
...And finally, my Global.asax configuration is set up like so:
protected void Application_Start()
{
GlobalConfiguration.Configure(WebApiConfig.Register);
RouteConfig.RegisterRoutes(RouteTable.Routes);
BundleConfig.RegisterBundles(BundleTable.Bundles);
}
...But one small problem.
When I navigate to http://x/api/GameSettings/audio, I get a 404 error. It's as if the category argument in the request isn't being properly associated to the Get(string category) method on my controller. This leads me to believe my routes are wrong or I'm missing something.
As a sanity check, I tested the route using a non-RESTful syntax, http://x/api/GameSettings?category=audio, which hit a breakpoint and yielded a result. This only reaffirms my theory that the WebAPI routing is off.
As an additional sanity check, I tested http://x/api/GameSettings/ and not only hit a breakpoint set in that function, but returned the expected result.
Question: What is my routing missing, that will allow http://x/api/GameSettings/audio to work like http://x/api/GameSettings?category=audio? I haven't worked with a RESTful API in a while, so I'm sure I'm missing something really dumb.

I would try to use the attribute routing. I believe that should work well for your scenario.
[RoutePrefix("api/GameSettings")]
public class GameSettingsController
{
// GET /api/GameSettings
[HttpGet]
public HttpResponseMessage Get()
{
// Magic
return Request.CreateResponse(HttpStatusCode.OK, model);
}
[Route("{category}")]
[HttpGet]
public HttpResponseMessage Get(string category)
{
// Similar.
}
[Route("{category}/{key}")]
[HttpGet]
public HttpResponseMessage Get(string category, string key)
{
// Slightly different, but still similar.
}
}
I would remove the stuff that you have added to the config.
Hope this helps.

Change the order and try.Because ASP.NET realizes that you have three routes. It will check the top-most route first and if your data can be placed in that route it will not check any more routes.
config.MapHttpAttributeRoutes();
config.Routes.MapHttpRoute(
name: "ApiKeyCommands",
routeTemplate: "api/{controller}/{category}/{key}",
defaults: new { controller = "GameSettings", category = "master" },
constraints: new { key = "[a-z0-9.-]" }
);
config.Routes.MapHttpRoute(
name: "ApiCategoryCommands",
routeTemplate: "api/{controller}/{category})",
defaults: new { controller = "GameSettings" }
);
config.Routes.MapHttpRoute(
name: "ApiGeneralCommand",
routeTemplate: "api/{controller}",
defaults: new { controller = "GameSettings" }
);

Custom method names in ASP.NET Web API

I'm converting from the WCF Web API to the new ASP.NET MVC 4 Web API. I have a UsersController, and I want to have a method named Authenticate. I see examples of how to do GetAll, GetOne, Post, and Delete, however what if I want to add extra methods into these services? For instance, my UsersService should have a method called Authenticate where they pass in a username and password, however it doesn't work.
public class UsersController : BaseApiController
{
public string GetAll()
{
return "getall!";
}
public string Get(int id)
{
return "get 1! " + id;
}
public User GetAuthenticate(string userName, string password, string applicationName)
{
LogWriter.Write(String.Format("Received authenticate request for username {0} and password {1} and application {2}",
userName, password, applicationName));
//check if valid leapfrog login.
var decodedUsername = userName.Replace("%40", "#");
var encodedPassword = password.Length > 0 ? Utility.HashString(password) : String.Empty;
var leapFrogUsers = LeapFrogUserData.FindAll(decodedUsername, encodedPassword);
if (leapFrogUsers.Count > 0)
{
return new User
{
Id = (uint)leapFrogUsers[0].Id,
Guid = leapFrogUsers[0].Guid
};
}
else
throw new HttpResponseException("Invalid login credentials");
}
}
I can browse to myapi/api/users/ and it will call GetAll and I can browse to myapi/api/users/1 and it will call Get, however if I call myapi/api/users/authenticate?username={0}&password={1} then it will call Get (NOT Authenticate) and error:
The parameters dictionary contains a null entry for parameter 'id' of non-nullable type 'System.Int32' for method 'System.String Get(Int32)' in 'Navtrak.Services.WCF.NavtrakAPI.Controllers.UsersController'. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter.
How can I call custom method names such as Authenticate?

By default the route configuration follows RESTFul conventions meaning that it will accept only the Get, Post, Put and Delete action names (look at the route in global.asax => by default it doesn't allow you to specify any action name => it uses the HTTP verb to dispatch). So when you send a GET request to /api/users/authenticate you are basically calling the Get(int id) action and passing id=authenticate which obviously crashes because your Get action expects an integer.
If you want to have different action names than the standard ones you could modify your route definition in global.asax:
Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{action}/{id}",
defaults: new { action = "get", id = RouteParameter.Optional }
);
Now you can navigate to /api/users/getauthenticate to authenticate the user.

This is the best method I have come up with so far to incorporate extra GET methods while supporting the normal REST methods as well. Add the following routes to your WebApiConfig:
routes.MapHttpRoute("DefaultApiWithId", "Api/{controller}/{id}", new { id = RouteParameter.Optional }, new { id = #"\d+" });
routes.MapHttpRoute("DefaultApiWithAction", "Api/{controller}/{action}");
routes.MapHttpRoute("DefaultApiGet", "Api/{controller}", new { action = "Get" }, new { httpMethod = new HttpMethodConstraint(HttpMethod.Get) });
routes.MapHttpRoute("DefaultApiPost", "Api/{controller}", new {action = "Post"}, new {httpMethod = new HttpMethodConstraint(HttpMethod.Post)});
I verified this solution with the test class below. I was able to successfully hit each method in my controller below:
public class TestController : ApiController
{
public string Get()
{
return string.Empty;
}
public string Get(int id)
{
return string.Empty;
}
public string GetAll()
{
return string.Empty;
}
public void Post([FromBody]string value)
{
}
public void Put(int id, [FromBody]string value)
{
}
public void Delete(int id)
{
}
}
I verified that it supports the following requests:
GET /Test
GET /Test/1
GET /Test/GetAll
POST /Test
PUT /Test/1
DELETE /Test/1
Note That if your extra GET actions do not begin with 'Get' you may want to add an HttpGet attribute to the method.

I am days into the MVC4 world.
For what its worth, I have a SitesAPIController, and I needed a custom method, that could be called like:
http://localhost:9000/api/SitesAPI/Disposition/0
With different values for the last parameter to get record with different dispositions.
What Finally worked for me was:
The method in the SitesAPIController:
// GET api/SitesAPI/Disposition/1
[ActionName("Disposition")]
[HttpGet]
public Site Disposition(int disposition)
{
Site site = db.Sites.Where(s => s.Disposition == disposition).First();
return site;
}
And this in the WebApiConfig.cs
// this was already there
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
// this i added
config.Routes.MapHttpRoute(
name: "Action",
routeTemplate: "api/{controller}/{action}/{disposition}"
);
For as long as I was naming the {disposition} as {id} i was encountering:
{
"Message": "No HTTP resource was found that matches the request URI 'http://localhost:9000/api/SitesAPI/Disposition/0'.",
"MessageDetail": "No action was found on the controller 'SitesAPI' that matches the request."
}
When I renamed it to {disposition} it started working. So apparently the parameter name is matched with the value in the placeholder.
Feel free to edit this answer to make it more accurate/explanatory.

Web Api by default expects URL in the form of api/{controller}/{id}, to override this default routing. you can set routing with any of below two ways.
First option:
Add below route registration in WebApiConfig.cs
config.Routes.MapHttpRoute(
name: "CustomApi",
routeTemplate: "api/{controller}/{action}/{id}",
defaults: new { id = RouteParameter.Optional }
);
Decorate your action method with HttpGet and parameters as below
[HttpGet]
public HttpResponseMessage ReadMyData(string param1,
string param2, string param3)
{
// your code here
}
for calling above method url will be like below
http://localhost:[yourport]/api/MyData/ReadMyData?param1=value1&param2=value2&param3=value3
Second option
Add route prefix to Controller class and Decorate your action method with HttpGet as below.
In this case no need change any WebApiConfig.cs. It can have default routing.
[RoutePrefix("api/{controller}/{action}")]
public class MyDataController : ApiController
{
[HttpGet]
public HttpResponseMessage ReadMyData(string param1,
string param2, string param3)
{
// your code here
}
}
for calling above method url will be like below
http://localhost:[yourport]/api/MyData/ReadMyData?param1=value1&param2=value2&param3=value3

In case you're using ASP.NET 5 with ASP.NET MVC 6, most of these answers simply won't work because you'll normally let MVC create the appropriate route collection for you (using the default RESTful conventions), meaning that you won't find any Routes.MapRoute() call to edit at will.
The ConfigureServices() method invoked by the Startup.cs file will register MVC with the Dependency Injection framework built into ASP.NET 5: that way, when you call ApplicationBuilder.UseMvc() later in that class, the MVC framework will automatically add these default routes to your app. We can take a look of what happens behind the hood by looking at the UseMvc() method implementation within the framework source code:
public static IApplicationBuilder UseMvc(
[NotNull] this IApplicationBuilder app,
[NotNull] Action<IRouteBuilder> configureRoutes)
{
// Verify if AddMvc was done before calling UseMvc
// We use the MvcMarkerService to make sure if all the services were added.
MvcServicesHelper.ThrowIfMvcNotRegistered(app.ApplicationServices);
var routes = new RouteBuilder
{
DefaultHandler = new MvcRouteHandler(),
ServiceProvider = app.ApplicationServices
};
configureRoutes(routes);
// Adding the attribute route comes after running the user-code because
// we want to respect any changes to the DefaultHandler.
routes.Routes.Insert(0, AttributeRouting.CreateAttributeMegaRoute(
routes.DefaultHandler,
app.ApplicationServices));
return app.UseRouter(routes.Build());
}
The good thing about this is that the framework now handles all the hard work, iterating through all the Controller's Actions and setting up their default routes, thus saving you some redundant work.
The bad thing is, there's little or no documentation about how you could add your own routes. Luckily enough, you can easily do that by using either a Convention-Based and/or an Attribute-Based approach (aka Attribute Routing).
Convention-Based
In your Startup.cs class, replace this:
app.UseMvc();
with this:
app.UseMvc(routes =>
{
// Route Sample A
routes.MapRoute(
name: "RouteSampleA",
template: "MyOwnGet",
defaults: new { controller = "Items", action = "Get" }
);
// Route Sample B
routes.MapRoute(
name: "RouteSampleB",
template: "MyOwnPost",
defaults: new { controller = "Items", action = "Post" }
);
});
Attribute-Based
A great thing about MVC6 is that you can also define routes on a per-controller basis by decorating either the Controller class and/or the Action methods with the appropriate RouteAttribute and/or HttpGet / HttpPost template parameters, such as the following:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNet.Mvc;
namespace MyNamespace.Controllers
{
[Route("api/[controller]")]
public class ItemsController : Controller
{
// GET: api/items
[HttpGet()]
public IEnumerable<string> Get()
{
return GetLatestItems();
}
// GET: api/items/5
[HttpGet("{num}")]
public IEnumerable<string> Get(int num)
{
return GetLatestItems(5);
}
// GET: api/items/GetLatestItems
[HttpGet("GetLatestItems")]
public IEnumerable<string> GetLatestItems()
{
return GetLatestItems(5);
}
// GET api/items/GetLatestItems/5
[HttpGet("GetLatestItems/{num}")]
public IEnumerable<string> GetLatestItems(int num)
{
return new string[] { "test", "test2" };
}
// POST: /api/items/PostSomething
[HttpPost("PostSomething")]
public IActionResult Post([FromBody]string someData)
{
return Content("OK, got it!");
}
}
}
This controller will handle the following requests:
[GET] api/items
[GET] api/items/5
[GET] api/items/GetLatestItems
[GET] api/items/GetLatestItems/5
[POST] api/items/PostSomething
Also notice that if you use the two approaches togheter, Attribute-based routes (when defined) would override Convention-based ones, and both of them would override the default routes defined by UseMvc().
For more info, you can also read the following post on my blog.

See this article for a longer discussion of named actions. It also shows that you can use the [HttpGet] attribute instead of prefixing the action name with "get".
http://www.asp.net/web-api/overview/web-api-routing-and-actions/routing-in-aspnet-web-api

Web APi 2 and later versions support a new type of routing, called attribute routing. As the name implies, attribute routing uses attributes to define routes. Attribute routing gives you more control over the URIs in your web API. For example, you can easily create URIs that describe hierarchies of resources.
For example:
[Route("customers/{customerId}/orders")]
public IEnumerable<Order> GetOrdersByCustomer(int customerId) { ... }
Will perfect and you don't need any extra code for example in WebApiConfig.cs.
Just you have to be sure web api routing is enabled or not in WebApiConfig.cs , if not you can activate like below:
// Web API routes
config.MapHttpAttributeRoutes();
You don't have to do something more or change something in WebApiConfig.cs. For more details you can have a look this article.

Just modify your WebAPIConfig.cs as bellow
Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{action}/{id}",
defaults: new { action = "get", id = RouteParameter.Optional });
Then implement your API as bellow
// GET: api/Controller_Name/Show/1
[ActionName("Show")]
[HttpGet]
public EventPlanner Id(int id){}