在.net core中，使用WebApiClient去調用restful Api的接口

原文鏈接：https://www.c-sharpcorner.com/article/using-webapiclient-to-call-rest-apis-in-net-core/

Create Some APIs 

Here I use ASP.NET Core WebAPI to creat some RESTful APIs.

1. [Route("api/[controller]")]  
2. public class PersonsController : Controller  
3. {  
4.     // GET: api/persons  
5.     [HttpGet]  
6.     public IEnumerable<Person> Get()  
7.     {  
8.         return new List<Person>  
9.         {  
10.             new Person{Id = 1 , Name = "catcher wong"},  
11.             new Person{Id = 2 , Name = "james"}  
12.         };  
13.     }  
14.   
15.     // GET api/persons/5  
16.     [HttpGet("{id}")]  
17.     public Person Get(int id)  
18.     {  
19.         return new Person { Id = id, Name = "name" };  
20.     }  
21.   
22.     // POST api/persons  
23.     [HttpPost]  
24.     public Person Post([FromBody]Person person)  
25.     {  
26.         if (person == null) return new Person();  
27.   
28.         return new Person { Id = person.Id, Name = person.Name };  
29.     }  
30.   
31.     // PUT api/persons/  
32.     [HttpPut]  
33.     public string Put([FromBody]int id)  
34.     {  
35.         return $"put {id}";  
36.     }  
37.   
38.     // DELETE api/persons/5  
39.     [HttpDelete("{id}")]  
40.     public string Delete(int id)  
41.     {  
42.         return $"del {id}";  
43.     }  
44. }  

Interface Declaration

Create an interface named IPersonApiClient which inherit from IHttpApiClient.

1. public interface IPersonApiClient : IHttpApiClient { }  

Add some methods that need to call APIs.

Every method must have a HTTP attribute that provides the request method and relative URL. The return type should be ITask<T>.

1. [HttpGet("/api/persons")]    
2. ITask<List<Person>> GetPersonsAsync();    

A request URL can be updated dynamically using replacement blocks and parameters on the method. A replacement block is an alphanumeric string surrounded by { and }.

1. [HttpGet("/api/persons/{id}")]  
2. ITask<Person> GetPersonAsync(int id);  

When our requst parameters should in request body, we can use some attributes to specify the content, such as JsonContent, FormContent .etc.

1. [HttpPost("/api/persons")]  
2. ITask<Person> AddPersonAsync([JsonContent]Person person);   

The following code demonstrates the basic usage.

1. public interface IPersonApiClient : IHttpApiClient  
2. {  
3.     [HttpGet("/api/persons")]  
4.     ITask<List<Person>> GetPersonsAsync();  
5.   
6.     [HttpGet("/api/persons/{id}")]  
7.     ITask<Person> GetPersonAsync(int id);  
8.   
9.     [HttpPost("/api/persons")]  
10.     ITask<Person> AddPersonAsync([JsonContent]Person person);  
11.   
12.     [HttpPut("/api/persons")]  
13.     ITask<string> EditPersonAsync([JsonContent]int id);  
14.   
15.     [HttpDelete("/api/persons/{id}")]  
16.     ITask<string> DeletePersonAsync(int id);  
17. }  

The next step is how to retrieve the response of the request.

Retrieving Response

We should create a client first. After creating , what we need to do is call the methods we declared in the interface.

1. //specify the config  
2. var config = new HttpApiConfig  
3. {                  
4.     HttpHost = new Uri("http://localhost:9999"),  
5. };  
6.   
7. var client = HttpApiClient.Create<IPersonApiClient>(config);  
8.   
9. var persons = await client.GetPersonsAsync();  
10.   
11. Console.WriteLine("GetPersonsAsync result:");  
12. foreach (var item in persons)  
13. {  
14.     Console.WriteLine($"{item.Id}-{item.Name}");  
15. }  
16.   
17. var person = await client.GetPersonAsync(1000);  
18. Console.WriteLine("GetPersonAsync result:");  
19. Console.WriteLine($"{person.Id}-{person.Name}");  
20.   
21.   
22. var newPerson = new Person { Id = 999, Name = "999" };  
23. var postResult = await client.AddPersonAsync(newPerson);  
24. Console.WriteLine("AddPersonAsync result:");  
25. Console.WriteLine($"{postResult.Id}-{postResult.Name}");  
26.   
27.   
28. var editResult = await client.EditPersonAsync(1);  
29. Console.WriteLine("EditPersonAsync result:");  
30. Console.WriteLine($"{editResult}");  
31.   
32. var delResult = await client.DeletePersonAsync(1);  
33. Console.WriteLine("DeletePersonAsync result:");  
34. Console.WriteLine($"{delResult}");