| uid | title | author | description | ms.author | ms.date | ms.assetid | msc.legacyurl | msc.type |
|---|---|---|---|---|---|---|---|---|
web-api/overview/odata-support-in-aspnet-web-api/odata-v4/create-an-odata-v4-endpoint |
Create an OData v4 Endpoint Using ASP.NET Web API 2.2 | Microsoft Docs |
rick-anderson |
The Open Data Protocol (OData) is a data access protocol for the web. OData provides a uniform way to query and manipulate data sets through CRUD operations... |
riande |
01/23/2019 |
1e1927c0-ded1-4752-80fd-a146628d2f09 |
/web-api/overview/odata-support-in-aspnet-web-api/odata-v4/create-an-odata-v4-endpoint |
authoredcontent |
The Open Data Protocol (OData) is a data access protocol for the web. OData provides a uniform way to query and manipulate data sets through CRUD operations (create, read, update, and delete).
ASP.NET Web API supports both v3 and v4 of the protocol. You can even have a v4 endpoint that runs side-by-side with a v3 endpoint.
This tutorial shows how to create an OData v4 endpoint that supports CRUD operations.
- Web API 5.2
- OData v4
- Visual Studio 2017 (download Visual Studio 2017 here)
- Entity Framework 6
- .NET 4.7.2
For the OData Version 3, see Creating an OData v3 Endpoint.
In Visual Studio, from the File menu, select New > Project.
Expand Installed > Visual C# > Web, and select the ASP.NET Web Application (.NET Framework) template. Name the project "ProductService".
Select OK.
Select the Empty template. Under Add folders and core references for:, select Web API. Select OK.
From the Tools menu, select NuGet Package Manager > Package Manager Console. In the Package Manager Console window, type:
[!code-consoleMain]
This command installs the latest OData NuGet packages.
A model is an object that represents a data entity in your application.
In Solution Explorer, right-click the Models folder. From the context menu, select Add > Class.
Note
By convention, model classes are placed in the Models folder, but you don't have to follow this convention in your own projects.
Name the class Product. In the Product.cs file, replace the boilerplate code with the following:
[!code-csharpMain]
The Id property is the entity key. Clients can query entities by key. For example, to get the product with ID of 5, the URI is /Products(5). The Id property will also be the primary key in the back-end database.
For this tutorial, we'll use Entity Framework (EF) Code First to create the back-end database.
Note
Web API OData does not require EF. Use any data-access layer that can translate database entities into models.
First, install the NuGet package for EF. From the Tools menu, select NuGet Package Manager > Package Manager Console. In the Package Manager Console window, type:
[!code-consoleMain]
Open the Web.config file, and add the following section inside the configuration element, after the configSections element.
[!code-xmlMain]
This setting adds a connection string for a LocalDB database. This database will be used when you run the app locally.
Next, add a class named ProductsContext to the Models folder:
[!code-csharpMain]
In the constructor, "name=ProductsContext" gives the name of the connection string.
Open the file App_Start/WebApiConfig.cs. Add the following using statements:
[!code-csharpMain]
Then add the following code to the Register method:
[!code-csharpMain]
This code does two things:
- Creates an Entity Data Model (EDM).
- Adds a route.
An EDM is an abstract model of the data. The EDM is used to create the service metadata document. The ODataConventionModelBuilder class creates an EDM by using default naming conventions. This approach requires the least code. If you want more control over the EDM, you can use the ODataModelBuilder class to create the EDM by adding properties, keys, and navigation properties explicitly.
A route tells Web API how to route HTTP requests to the endpoint. To create an OData v4 route, call the MapODataServiceRoute extension method.
If your application has multiple OData endpoints, create a separate route for each. Give each route a unique route name and prefix.
A controller is a class that handles HTTP requests. You create a separate controller for each entity set in your OData service. In this tutorial, you will create one controller, for the Product entity.
In Solution Explorer, right-click the Controllers folder and select Add > Class. Name the class ProductsController.
Note
The version of this tutorial for OData v3 uses the Add Controller scaffolding. Currently, there is no scaffolding for OData v4.
Replace the boilerplate code in ProductsController.cs with the following.
[!code-csharpMain]
The controller uses the ProductsContext class to access the database using EF. Notice that the controller overrides the Dispose method to dispose of the ProductsContext.
This is the starting point for the controller. Next, we'll add methods for all of the CRUD operations.
Add the following methods to ProductsController.
[!code-csharpMain]
The parameterless version of the Get method returns the entire Products collection. The Get method with a key parameter looks up a product by its key (in this case, the Id property).
The [EnableQuery] attribute enables clients to modify the query, by using query options such as $filter, $sort, and $page. For more information, see Supporting OData Query Options.
To enable clients to add a new product to the database, add the following method to ProductsController.
[!code-csharpMain]
OData supports two different semantics for updating an entity, PATCH and PUT.
- PATCH performs a partial update. The client specifies just the properties to update.
- PUT replaces the entire entity.
The disadvantage of PUT is that the client must send values for all of the properties in the entity, including values that are not changing. The OData spec states that PATCH is preferred.
In any case, here is the code for both PATCH and PUT methods:
[!code-csharpMain]
In the case of PATCH, the controller uses the Delta<T> type to track the changes.
To enable clients to delete a product from the database, add the following method to ProductsController.
[!code-csharpMain]