In this post, I would like to share details about the changes and usages of the attribute routing in OData ASP.NET Core OData 8.0 RC. The code\nsnippets in this post are from this<\/a> sample project. Please try and let me know your thoughts.<\/p>\n In the \u201chistory\u201d of ASP.NET Core OData, such as 6.x and 7.x version, OData attribute routing\u00a0<\/strong>uses two\u00a0attributes\u00a0to find\u00a0controller\u00a0and\u00a0action. One is ODataRoutePrefixAttribute<\/strong>, the other is\u00a0ODataRouteAttribute<\/strong>. Here’s a basic usage to define an OData attribute routing:<\/p>\n In ASP.NET Core OData 8.0 RC, these two attributes are gone<\/strong>.<\/p>\n Instead, OData attribute routing is changed to use ASP.NET Core route template attribute classes. ASP.NET Core has the following route template attributes:<\/p>\n Switch to use ASP.NET Core route attributes is straightforward. Here\u2019s the same OData route template using HttpGetAttribute<\/strong>:<\/p>\n Be noted, Head HTTP method is not supported yet in RC.<\/p>\n To enable OData attribute routing to work, either controller or action should decorate an attribute named ODataRoutingAttribute<\/strong>. [It’s renamed as ODataAttributeRoutingAttribute<\/strong> in 8.0.]<\/p>\n ODataRoutingAttribute<\/strong> is introduced in RC version to avoid polluting other ASP.NET Core route templates, since OData attribute routing is enabled by default if call ODataRoutingAttribute<\/strong> can be used on controller and action. If we decorate it on the controller, all actions in this controller are considered as OData actions. That means the attribute routing convention will parse all routing templates as OData attribute routing. For example:<\/p>\n We can decorate a specific action using ODataRoutingAttribute<\/strong> as:<\/p>\n Where:<\/p>\n If you run and test using following requests:<\/p>\n 1) GET http:\/\/localhost:5000\/odata\/Orders\/2<\/em><\/p>\n The response is OData payload:<\/p>\n 2) GET http:\/\/localhost:5000\/odata\/Orders(3)<\/em><\/p>\n The response is a plain text string:<\/p>\n ODataController<\/strong> has ODataRoutingAttribute<\/strong> decorated as:<\/p>\n So, to create your own controller and derived it from ODataController<\/strong> is a common way to use OData attribute routing. Here is an example:<\/p>\n Starting from next section, let’s review some OData attribute routing scenarios.<\/p>\n The basic attribute routing scenario is to use HTTP Verb attributes directly.<\/p>\n Let us have the following controller as example (Be noted<\/strong>, we use In the above codes, where:<\/p>\n Based on the preceding route templates,<\/p>\n Be noted<\/strong><\/span>, don’t forget to append the route prefix when you construct the route template.<\/p>\n We can decorate RouteAttribute<\/strong> on action and combine it with Http Verb attributes.<\/p>\n Let us have the following controller as example:<\/p>\n In this controller, OperationBook(int key)<\/strong> has two HTTP Verb attributes, [HttpPatch]<\/strong> and [HttpDelete]<\/strong>. Both have null<\/strong> route template. It also has a RouteAttribute<\/strong> with route template string. Therefore, [Route(“odata\/Books({key})”)]<\/strong> is combined with patch and delete verb attributes to construct the following route template (From the sample<\/a>, you can send \u201c~\/$odata\u201d to get the following debug information):<\/p>\n Based on the route template, The Uri path Patch ~\/odata\/Books(2)<\/em> can match this action and bind the key value 2 to the key<\/strong> parameter.<\/p>\n We can decorate RouteAttribute<\/strong> on the controller. The route template in [Route] attribute is combined with route template on the individual action in that controller. The\nroute template of RouteAttribute<\/strong> is prepended before route template on the action to form the final route template for that action.<\/p>\n Let us have the following controller as example (be noted, I use ODataRouting<\/strong> on the controller):<\/p>\n Where:<\/p>\n Based on the attribute routing templates:<\/p>\n We can also decorate multiple RouteAttribute<\/strong> on the controller. It means that route template of each [Route] combines with each of the route template of attributes on the action methods:<\/p>\n Let us have the following controller as example (be noted, I use ODataRouting<\/strong> on the action):<\/p>\n So, Get(string version)<\/strong> has two attribute routing templates:<\/p>\n Based on the implementation of 1) GET http:\/\/localhost:5000\/odata\/Orders<\/em><\/p>\n The response is:<\/p>\n 2) GET http:\/\/localhost:5000\/v2001\/Orders<\/em><\/p>\n The response is:<\/p>\n We can use “\/” to suppress prepending the RouteAttribute<\/strong> on controller to individual action.<\/p>\n Let us have the following controller as example:<\/p>\n Where, SendTo(\u2026)<\/strong> action has one route template as:<\/p>\n ~\/odata\/orders({key})\/SendTo(lat={lat},lon={lon})<\/strong><\/p>\n Clearly, “v{version}” in Known issue<\/strong>: If we use two [Route(\u2026)] on HandAbolusteController, SendTo<\/strong> will have two selector models associated and ASP.NET Core throws ambiguous selector exception. It\u2019s a known issue and will fix in the next version.<\/p>\n We can use [NonODataController]<\/strong> and [NonODataAction]<\/strong> to exclude certain controller or action out of attribute routing. [Both are replaced by ODataIgnoredAttribute<\/strong> in 8.0.]<\/p>\n Besides, [ODataModelAttribute] (<\/strong>renamed as ODataRouteComponentAttribute<\/strong> in 8.0)<\/strong>\u00a0has no effect to attribute routing, it’s only for the conventional routing to specify the route prefix.\nIn attribute routing, we put the route prefix in the route template directly, either using [Route] attribute or prepend the route prefix before the route template, such as “odata” prefix in route template “odata\/Books”.<\/p>\n We can also disable the attribute routing globally using EnableAttributeRouting<\/strong> property on ODataOptions<\/strong>.<\/p>\n As mentioned in Routing in ASP.NET Core OData 8.0 Preview<\/a>, OData attribute routing is also a “conventional routing”, because the template string in the attribute should follow up the OData URL convention<\/a>. Here’s the definition of AttributeRoutingConvention<\/strong>:<\/p>\n Where,\n IODataPathTemplateParser<\/strong> is registered in the service provider. It can inject into the constructor of AttributeRoutingConvention<\/strong>. The default route template parser uses the built-in OData Uri parser to parse the route template path. If it can’t meet your requirement, you can create your own template parser to overwrite the default one.<\/p>\n Attribute routing enables you to achieve more routings by constructing basic and advanced OData routing templates. Moreover, you can mix it with conventional routing to achieve more. Again, to improve OData Web API routing is never stopped. We are still looking forward to feedbacks, requirements and concerns to improve the routing design and implementation. Please do not hesitate to try and let me know your thoughts through\u00a0saxu@microsoft.com<\/a>. Thanks.<\/p>\n Great thanks for Javier Calvarro Nelson<\/a> and David Fowler<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":" Introduction Attribute routing is how Web API matches the incoming HTTP requests to an action based on route template attributes decorated on controller or action. ASP.NET Core defines a set of route template attributes to enable attribute routing, such as RouteAttribute, HttpGetAttribute etc. ASP.NET Core OData 8.0 RC supports these attributes to enable you to […]<\/p>\n","protected":false},"author":514,"featured_media":3253,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1472,1,117],"tags":[502,1471,48],"class_list":["post-4407","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-asp-net-core","category-odata","category-webapi","tag-asp-net-core","tag-attribute-routing","tag-odata"],"acf":[],"blog_post_summary":" Introduction Attribute routing is how Web API matches the incoming HTTP requests to an action based on route template attributes decorated on controller or action. ASP.NET Core defines a set of route template attributes to enable attribute routing, such as RouteAttribute, HttpGetAttribute etc. ASP.NET Core OData 8.0 RC supports these attributes to enable you to […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/posts\/4407","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/users\/514"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/comments?post=4407"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/posts\/4407\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/media\/3253"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/media?parent=4407"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/categories?post=4407"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/tags?post=4407"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}No ODataRouteAttribute and ODataRoutePrefixAttribute<\/h2>\n
[ODataRoute(\"Books({key})\")]\r\npublic IActionResult Get(int key)\r\n{\r\n \u2026\r\n}\r\n<\/pre>\n\n
[ODataRoute(\"Books({key})\")]<\/s>\r\n[HttpGet(\"Books({key})\")]\r\npublic IActionResult Get(int key)\r\n{\r\n \u2026\r\n}\r\n<\/pre>\nODataRoutingAttribute<\/h2>\n
AddOData()<\/code>.<\/p>\n[ODataRouting]\r\npublic class HandleCustomerController : Controller\r\n{\r\n\u2026\r\n}\r\n<\/pre>\npublic class HandleOthersController : Controller\r\n{\r\n [ODataRouting]\r\n [HttpGet(\"odata\/Orders\/{key}\")]\r\n public IActionResult Get(int key)\r\n {\r\n return Ok($\"Orders{key} from OData\");\r\n }\r\n\r\n [HttpGet(\"odata\/Orders({key})\")]\r\n public IActionResult GetOrder(int key)\r\n {\r\n return Ok($\"Orders{key} from non-OData\");\r\n }\r\n}\r\n<\/pre>\n\n
[ODataRouting]<\/code> and the route template \u201cOrders\/{key}\u201d is a valid OData template.<\/li>\n{\r\n \"@odata.context\": \"http:\/\/localhost:5000\/odata\/$metadata#Edm.String\",\r\n \"value\": \"Orders2 from OData\"\r\n}\r\n<\/pre>\nOrders3 from non-OData<\/pre>\n
ODataController<\/h2>\n
[ODataRouting]\r\npublic abstract class ODataController : ControllerBase\r\n{}\r\n<\/pre>\npublic class HandleBookController : ODataController\r\n{}\r\n<\/pre>\nAttribute routing using Http Verb attributes<\/h2>\n
ODataController<\/code> directly):<\/p>\npublic class HandleBookController : ODataController\r\n{\r\n [EnableQuery(PageSize = 1)]\r\n [HttpGet(\"odata\/Books\")]\r\n [HttpGet(\"odata\/Books\/$count\")]\r\n public IActionResult Get()\r\n {\r\n return Ok(_db.Books);\r\n }\r\n\r\n [EnableQuery]\r\n [HttpGet(\"odata\/Books({id})\")]\r\n [HttpGet(\"odata\/Books\/{id}\")]\r\n public IActionResult Get(int id)\r\n {\r\n return Ok(_db.Books.FirstOrDefault(c => c.Id == id));\r\n }\r\n}\r\n<\/pre>\n\n
int id<\/code> parameter.<\/li>\n<\/ul>\n\n
Attribute routing using Http Verb and Route attributes<\/h2>\n
public class HandleBookController : ODataController\r\n{\r\n [Route(\"odata\/Books({key})\")]\r\n [HttpPatch]\r\n [HttpDelete]\r\n public IActionResult OperationBook(int key)\r\n {\r\n \/\/ the return is just for test.\r\n return Ok(_db.Books.FirstOrDefault(c => c.Id == key));\r\n }\r\n}\r\n<\/pre>\n![](\"https:\/\/devblogs.microsoft.com\/odata\/wp-content\/uploads\/sites\/23\/2021\/03\/word-image.png\")
<\/p>\nAttribute routing using RouteAttribute on controller<\/h2>\n
[ODataRouting]\r\n[Route(\"v{version}\")]\r\npublic class HandleCustomerController : Controller\r\n{\r\n [HttpGet(\"Customers\")]\r\n [HttpGet(\"Customers\/$count\")]\r\n public IActionResult Get(string version)\r\n {\r\n return Ok(_db.Customers);\r\n }\r\n\r\n [HttpGet(\"Customers\/{key}\/Default.PlayPiano(kind={kind},name={name})\")]\r\n [HttpGet(\"Customers\/{key}\/PlayPiano(kind={kind},name={name})\")]\r\n public string LetUsPlayPiano(string version, int key, int kind, string name)\r\n {\r\n return $\"[{data}], Customer {key} is playing Piano (kind={kind},name={name}\";\r\n }\r\n}\r\n<\/pre>\n\n
RouteAttribute<\/code>, its route template string \u201cv{version}\u201d is prepended to route template on each individual action.<\/li>\n[HttpGet]<\/code> attributes, the route template in each [HttpGet] combines with the route template on the controller to build the following attribute routing templates:\n\n
[HttpGet]<\/code> attributes, the route template in each [HttpGet] combines with the route template on the controller to build the following attribute routing templates:\n\n
\n
Get(string version)<\/code>, where the value of version<\/strong> parameter is “2”.<\/li>\nLetUsPlayPiano(version, key, kind, name)<\/code>, where version<\/strong>=”2″, key<\/strong>=3, kind<\/strong>=4 and name<\/strong>=”Yep”.<\/li>\n<\/ul>\nMultiple RouteAttribute routes<\/h2>\n
[Route(\"odata\")]\r\n[Route(\"v{version}\")]\r\npublic class HandleMultipleController: Controller\r\n{\r\n [ODataRouting]\r\n [HttpGet(\"orders\")]\r\n public string Get(string version)\r\n {\r\n if (version != null)\r\n {\r\n return $\"Orders from version = {version}\";\r\n }\r\n else\r\n {\r\n return \"Orders from odata\";\r\n }\r\n }\r\n}\r\n<\/pre>\n\n
Get(string version)<\/code>, we can test it using following requests:<\/p>\n{\r\n \"@odata.context\":\u00a0\"http:\/\/localhost:5000\/odata\/$metadata#Edm.String\",\r\n \"value\":\u00a0\"Orders\u00a0from\u00a0odata\"\r\n}\r\n<\/pre>\n{\r\n \"@odata.context\":\u00a0\"http:\/\/localhost:5000\/v2001\/$metadata#Edm.String\",\r\n \"value\":\u00a0\"Orders\u00a0from\u00a0version\u00a0=\u00a02001\"\r\n}\r\n<\/pre>\nSuppress RouteAttribute on controller<\/h2>\n
[Route(\"v{version}\")]\r\npublic class HandAbolusteController: Controller\r\n{\r\n [ODataRouting]\r\n [HttpGet(\"\/odata\/orders({key})\/SendTo(lat={lat},lon={lon})\")]\r\n public string SendTo(int key, double lat, double lon)\r\n {\r\n return $\"Send Order({key}) to location at ({lat},{lon})\";\r\n }\r\n}\r\n<\/pre>\n[Route(\"v{version}\")]<\/code> doesn’t prepend to [HttpGet] attribute template.<\/p>\nOther Attributes<\/h2>\n
services.AddOData(opt => opt.EnableAttributeRouting = false);\r\n<\/pre>\n
Route template parser<\/h2>\n
public class AttributeRoutingConvention : IODataControllerActionConvention\r\n{\r\n public AttributeRoutingConvention(ILogger<AttributeRoutingConvention> logger,\r\n IODataPathTemplateParser parser)\r\n { ... }\r\n\r\n public virtual int Order => -100;\r\n \/\/ \u2026 \r\n}<\/pre>\nIODataPathTemplateParser<\/code> interface is a route template parser which is how OData parses and understands the route template string.<\/p>\npublic interface IODataPathTemplateParser\r\n{\r\n ODataPathTemplate Parse(IEdmModel model, string odataPath, IServiceProvider requestProvider);\r\n}\r\n<\/pre>\nSummary<\/h2>\n