Web Api 控制器 接口 操作返回类型

操作返回类型（ASP.NET Core Web API 中控制器操作的返回类型）  
响应数据格式（ASP.NET Core Web API 中响应数据的格式）  
Web API 2 的操作结果  
创建数据传输对象 (DTO)  
async 和 ASP.NET MVC    
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1、IHttpActionResult => json()
Json(T content)
Ok()
Ok(T content)
NotFound()
Content(HttpStatusCode statusCode, T value)
BadRequest()
Redirect(string location)

[HttpGet]
public IHttpActionResult GetAllGrade()
{
    var result = Mapper.Map>(_gradeRepo.GetList(x => x.Status != "D"));
    return Json(result);
}

2、HttpResponseMessage 直接转换成HTTP响应消息

public HttpResponseMessage Get()
{
    HttpResponseMessage response = Request.CreateResponse(HttpStatusCode .OK, "hello");
    response.Content = new StringContent ( "hello wep api", Encoding .Unicode);
    response.Headers.CacheControl = new CacheControlHeaderValue
    {
        MaxAge = TimeSpan .FromSeconds(600)
        };
    return response;
}

public Task ExecuteAsync(CancellationToken cancellationToken)
{
    var response = new HttpResponseMessage()
    {
        Content = new StringContent(_value),
        RequestMessage = _request
    };
    return Task.FromResult(response);
}

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3、其它类型
将序列化后的返回值写入响应的正文（Response Body）,并且返回 HTTP 状态码 200（OK）
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4、async Task

// GET api/Books/5
[ResponseType(typeof(BookDetailDTO))]
public async Task GetBook(int id)
{
    var book = await db.Books.Include(b => b.Author).Select(b =>
        new BookDetailDTO()
        {
            Id = b.Id,
            Title = b.Title,
            Year = b.Year,
            Price = b.Price,
            AuthorName = b.Author.Name,
            Genre = b.Genre
        }).SingleOrDefaultAsync(b => b.Id == id);
    if (book == null)
    {
        return NotFound();
    }

    return Ok(book);
}

public Task ExecuteAsync(CancellationToken cancellationToken)
{
    var response = new HttpResponseMessage()
    {
        Content = new StringContent(_value),
        RequestMessage = _request
    };
    return Task.FromResult(response);
}

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asp.net mvc

public async Task Index()
{
    var departments = db.Departments.Include(d => d.Administrator);
    return View(await departments.ToListAsync());
}

public async Task Details(int? id)
{
    if (id == null)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }
    Department department = await db.Departments.FindAsync(id);
    if (department == null)
    {
        return HttpNotFound();
    }
    return View(department);
}

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5、ASP.NET Core 提供以下 Web API 控制器操作返回类型选项
● 特定类型：如 string，自定义对象类型， IEnumerable，IAsyncEnumerable
● IActionResult：当操作中可能有多个 ActionResult 返回类型时，适合使用 IActionResult 返回类型
● ActionResult
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6、
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7、
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