In order to build APIs with ASP.NET Web API, follow these steps:
1. Right-click on the 'Controllers' folder in Solution Explorer and add a new folder.
2. Right-click on the newly created folder and add a controller. Use the 'Web API 2 Controller' template and name it 'CustomersController'.
3. Open the 'Global.asax.cs' file and add the line of code mentioned in the readme text at the beginning of the 'Application_Start' method. Make sure to import the 'System.Web.Http' namespace.
4. In the 'CustomersController' class, add different actions to perform different CRUD operations:
GetCustomers: Returns a list of customers.
GetCustomer: Returns a single customer based on the ID provided.
CreateCustomer: Creates a new customer and returns the newly created customer.
UpdateCustomer: Updates an existing customer based on the ID provided.
DeleteCustomer: Deletes an existing customer based on the ID provided.
5. Apply the necessary HTTP attributes to the actions to specify the type of HTTP request they respond to (e.g., HTTP GET, POST, PUT, DELETE).
6. Validate the input received from the client and perform the required operations using the application DB context.
7. Save the changes after each operation and test the API to ensure it is working correctly.
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