Once that\u2019s installed, let\u2019s go ahead and add OData services to our API.<\/p>\n
To do that, go to: Startup.cs file and add in this line of code in your ConfigureServices Function:<\/p>\n
services.AddOData();<\/pre>\nNow we need to enable the dependency injection support for ALL HTTP routes.<\/p>\n
To do that, in the same file Startup.cs let\u2019s go to the Configure function and add these two lines of code:<\/p>\n
app.UseMvc(routeBuilder => {\r\n\r\n\u00a0\u00a0\u00a0\u00a0 routeBuilder.EnableDependencyInjection();\r\n\r\n routeBuilder.Expand().Select().OrderBy().Filter();\r\n\r\n});<\/pre>\n <\/p>\n
The first line of code enables the dependency injection to inject OData services into your existing API controller.<\/p>\n
The second line of code determines which OData functionality you would like to enable your API consumers to use, we will talk about Expand, Select and OrderBy in details shortly after we complete the setup of OData on your project.<\/p>\n
The last line of code we would want to add is an annotation on top of your API controller method, in our example here, we have a StudentsController class that has a GetStudents method to server all the available students in our database.<\/p>\n
Now all we need to do is to add this annotation on top of your GetStudents endpoint as follows:<\/p>\n
[EnableQuery]<\/pre>\n <\/p>\n
So your controller method code should look like this:<\/p>\n
[HttpGet]\r\n\r\n[EnableQuery]\r\n\r\npublic IEnumerable<Student> GetStudents(){\r\n\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 return this.context.Students;\r\n\r\n}<\/pre>\nNow that the setup is done, let\u2019s test OData select, OrderBy and expand functionality.<\/p>\n
<\/p>\n
Select<\/h3>\n
On your favorite API testing software or simply in the browser since this is a GET endpoint, let\u2019s try to select only the properties that we care about from the students objects.<\/p>\n
If the students object consists of an ID, Name and we care only about the Name, we could call our endpoint like this:<\/p>\n
api\/students?$select=Name<\/pre>\nThe results will be a json list of students that only has the Name property displayed. try different combinations such as:<\/p>\n
api\/students?$select=ID,Name<\/pre>\nThe select functionality enables you to control and reshape the data to fit just your need, it makes a big difference when your objects hold large amounts of data, like image data for instance that you don\u2019t really need for a specific API call, or rich text that is contained within the same object, using select could be a great optimization technique to expedite API calls and response time.<\/p>\n
<\/p>\n
OrderBy<\/h3>\n
The next functionality here is the OrderBy, which allows you to order your students based on their names alphabetically or their scores, try to hit your endpoint as follows:<\/p>\n
api\/students?$orderby=Name<\/pre>\nYou can also do:<\/p>\n
api\/students?$orderby=Score desc<\/pre>\n <\/p>\n
Expand<\/h3>\n
One other functionality we want to test here is the expand. The expand functionality comes with a great advantage since it allows navigation across multiple entities.<\/p>\n
In our example here, Students and Schools are in a many-to-one relationship, we can pull the school every student belongs to by making an expand call like this:<\/p>\n
api\/students?$expand=School<\/pre>\nNow we get to see both students and their schools nested within the same list of objects.<\/p>\n
<\/p>\n
Filter<\/h3>\n
The last functionality here is the Filter. Filtering enables you to query for a specific data with a specific value, for instance, If I\u2019m looking for a student with the name Todd, all I have to do is to make an API call as follows:<\/p>\n
api\/students?$filter=Name eq \u2018Todd\u2019<\/pre>\nThe call will return all students that have the name Todd, you can be more specific with certain properties such as scores. For instance: if I want all students with scores greater than 100, I could make the following API call:<\/p>\n
api\/students?filter=Score gt 100<\/pre>\nThere are more features in OData that enables even more powerful API functionality that I urge you to explore such as MaxTop for pagination.<\/p>\n
<\/p>\n
Final Notes<\/h3>\n
Here are few things to understand about OData:<\/p>\n
\n- OData has no dependency whatsoever on the entity framework, it can come in handy with EF but it doesn\u2019t depend on it, here\u2019s a project that runs an OData API without EF: https:\/\/github.com\/hassanhabib\/ODataWithoutEF<\/a><\/li>\n
- OData can give you more optimization with EF if you use IQueryable as a data return type that IEnumerable since IQueryable only evaluates after the query is built and ready to be executed.<\/li>\n
- OData is much older than any other similar technology out there, it was released officially in 2007 and it has been around since then being used in large scale applications such as Microsoft Graph which feeds most of Microsoft Office products and XBOX in addition to Microsoft Windows.<\/li>\n<\/ol>\n
<\/p>\n
The Future of OData<\/h3>\n
OData team continues to improve the feature and make it even easier and simpler to use and consume on existing and new APIs with both ASP.NET Web API (classic) or ASP.NET Core and we are working on adding even more powerful features in the near future.<\/p>\n","protected":false},"excerpt":{"rendered":"
Summary In this article, I\u2019m going to show you how you can supercharge your existing ASP.NET Core APIs with OData to provide better experience for your API consumers with only 4 lines of code. For the purpose of this tutorial please clone our demo project WashingtonSchools so you can follow up and try the different […]<\/p>\n","protected":false},"author":3348,"featured_media":3286,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1,117],"tags":[],"class_list":["post-3280","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-odata","category-webapi"],"acf":[],"blog_post_summary":"
Summary In this article, I\u2019m going to show you how you can supercharge your existing ASP.NET Core APIs with OData to provide better experience for your API consumers with only 4 lines of code. For the purpose of this tutorial please clone our demo project WashingtonSchools so you can follow up and try the different […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/posts\/3280","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\/3348"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/comments?post=3280"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/posts\/3280\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/media\/3286"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/media?parent=3280"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/categories?post=3280"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/odata\/wp-json\/wp\/v2\/tags?post=3280"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}