本篇體驗使用HttpClient對ASP.NET Web API服務實現增刪改查。

創建ASP.NET Web API項目

新建項目，選擇"ASP.NET MVC 4 Web應用程序"。

選擇"Web API"。

在Models文件夾下創建Product類。

    public class Product    {public int Id { get; set; }public string Name { get; set; }public string Category { get; set; }public decimal Price { get; set; }    }

在Models文件夾下創建IProductRepository接口。

    public interface IProductRepository    {IEnumerable<Product> GetAll();Product Get(int id);Product Add(Product item);void Remove(int id);bool Update(Product item);    }

在Models文件夾下創建ProductRepository類，實現IProductRepository接口。

   public class ProductRepository : IProductRepository    {private List<Product> products = new List<Product>();private int _nextId = 1;public ProductRepository(){    Add(new Product() {Name = "product1", Category = "sports", Price = 88M});    Add(new Product() { Name = "product2", Category = "sports", Price = 98M });    Add(new Product() { Name = "product3", Category = "toys", Price = 58M });}public IEnumerable<Product> GetAll(){    return products;}public Product Get(int id){    return products.Find(p => p.Id == id);}public Product Add(Product item){    if (item == null)    {throw new ArgumentNullException("item");    }    item.Id = _nextId++;    products.Add(item);    return item;}public bool Update(Product item){    if (item == null)    {throw new ArgumentNullException("item");    }    int index = products.FindIndex(p => p.Id == item.Id);    if (index == -1)    {return false;    }    products.RemoveAt(index);    products.Add(item);    return true;}public void Remove(int id){    products.RemoveAll(p => p.Id == id);}    }

在Controllers文件夾下創建空的ProductController。

   public class ProductController : ApiController    {static readonly IProductRepository repository = new ProductRepository();//獲取所有public IEnumerable<Product> GetAllProducts(){    return repository.GetAll();}//根據id獲取public Product GetProduct(int id){    Product item = repository.Get(id);    if (item == null)    {throw new HttpResponseException(HttpStatusCode.NotFound);    }    return item;}//根據類別查找所有產品public IEnumerable<Product> GetProductsByCategory(string category){    returnrepository.GetAll().Where(p => string.Equals(p.Category, category, StringComparison.OrdinalIgnoreCase));}//創建產品public HttpResponseMessage PostProduct(Product item){    item = repository.Add(item);    var response = Request.CreateResponse(HttpStatusCode.Created, item);    string uri = Url.Link("DefaultApi", new {id = item.Id});    response.Headers.Location = new Uri(uri);    return response;}//更新產品public void PutProduct(int id, Product product){    product.Id = id;    if (!repository.Update(product))    {throw new HttpResponseException(HttpStatusCode.NotFound);    }}//刪除產品public void DeleteProduct(int id){    Product item = repository.Get(id);    if (item == null)    {throw new HttpResponseException(HttpStatusCode.NotFound);    }    repository.Remove(id);}    }

在瀏覽器中輸入：

http://localhost:1310/api/Product 獲取到所有產品
http://localhost:1310/api/Product/1 獲取編號為1的產品

使用HttpClient查詢某個產品

在同一個解決方案下創建一個控制臺程序。

依次點擊"工具"，"庫程序包管理器","程序包管理器控制臺"，輸入如下：

Install-Package Microsoft.AspNet.WebApi.Client

在控制臺程序下添加Product類，與ASP.NET Web API中的對應。

    public class Product    {public string Name { get; set; }public double Price { get; set; }public string Category { get; set; }     }

編寫如下：

static void Main(string[] args){    RunAsync().Wait();    Console.ReadKey();}static async Task RunAsync(){    using (var client = new HttpClient())    {//設置client.BaseAddress = new Uri("http://localhost:1310/");client.DefaultRequestHeaders.Accept.Clear();client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));//異步獲取數據HttpResponseMessage response = await client.GetAsync("/api/Product/1");if (response.IsSuccessStatusCode){    Product product = await response.Content.ReadAsAsync<Product>();    Console.WriteLine("{0}\t{1}元\t{2}",product.Name, product.Price, product.Category);}    }}

把控制臺項目設置為啟動項目。

HttpResponseMessage的IsSuccessStatusCode只能返回true或false，如果想讓響應拋出異常，需要使用EnsureSuccessStatusCode方法。

try{    HttpResponseMessage response = await client.GetAsync("/api/Product/1");    response.EnsureSuccessStatusCode();//此方法確保響應失敗拋出異常}catch(HttpRequestException ex){    //處理異常}

另外，ReadAsAsync方法，默認接收MediaTypeFormatter類型的參數，支持 JSON, XML, 和Form-url-encoded格式，如果想自定義MediaTypeFormatter格式，參照如下：

var formatters = new List<MediaTypeFormatter>() {    new MyCustomFormatter(),    new JsonMediaTypeFormatter(),    new XmlMediaTypeFormatter()};resp.Content.ReadAsAsync<IEnumerable<Product>>(formatters);

使用HttpClient查詢所有產品

       static void Main(string[] args){    RunAsync().Wait();    Console.ReadKey();}static async Task RunAsync(){    using (var client = new HttpClient())    {//設置client.BaseAddress = new Uri("http://localhost:1310/");client.DefaultRequestHeaders.Accept.Clear();client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));//異步獲取數據HttpResponseMessage response = await client.GetAsync("/api/Product");if (response.IsSuccessStatusCode){    IEnumerable<Product> products = await response.Content.ReadAsAsync<IEnumerable<Product>>();    foreach (var item in products)    {Console.WriteLine("{0}\t{1}元\t{2}", item.Name, item.Price, item.Category);    }    }    }}

使用HttpClient添加

       static void Main(string[] args){    RunAsync().Wait();    Console.ReadKey();}static async Task RunAsync(){    using (var client = new HttpClient())    {//設置client.BaseAddress = new Uri("http://localhost:1310/");client.DefaultRequestHeaders.Accept.Clear();client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));//添加var myProduct = new Product() { Name = "myproduct", Price = 88, Category = "other" };HttpResponseMessage response = await client.PostAsJsonAsync("api/Product", myProduct);//異步獲取數據response = await client.GetAsync("/api/Product");if (response.IsSuccessStatusCode){    IEnumerable<Product> products = await response.Content.ReadAsAsync<IEnumerable<Product>>();    foreach (var item in products)    {Console.WriteLine("{0}\t{1}元\t{2}", item.Name, item.Price, item.Category);    }    }    }}

使用HttpClient修改

       static void Main(string[] args){    RunAsync().Wait();    Console.ReadKey();}static async Task RunAsync(){    using (var client = new HttpClient())    {//設置client.BaseAddress = new Uri("http://localhost:1310/");client.DefaultRequestHeaders.Accept.Clear();client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));//添加 HTTP POSTvar myProduct = new Product() { Name = "myproduct", Price = 100, Category = "other" };HttpResponseMessage response = await client.PostAsJsonAsync("api/product", myProduct);if (response.IsSuccessStatusCode){    Uri pUrl = response.Headers.Location;    //修改 HTTP PUT    myProduct.Price = 80;   // Update price    response = await client.PutAsJsonAsync(pUrl, myProduct);}//異步獲取數據response = await client.GetAsync("/api/Product");if (response.IsSuccessStatusCode){    IEnumerable<Product> products = await response.Content.ReadAsAsync<IEnumerable<Product>>();    foreach (var item in products)    {Console.WriteLine("{0}\t{1}元\t{2}", item.Name, item.Price, item.Category);    }    }    }}

使用HttpClient刪除

static void Main(string[] args){    RunAsync().Wait();    Console.ReadKey();}static async Task RunAsync(){    using (var client = new HttpClient())    {//設置client.BaseAddress = new Uri("http://localhost:1310/");client.DefaultRequestHeaders.Accept.Clear();client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));//添加 HTTP POSTvar myProduct = new Product() { Name = "myproduct", Price = 100, Category = "other" };HttpResponseMessage response = await client.PostAsJsonAsync("api/product", myProduct);if (response.IsSuccessStatusCode){    Uri pUrl = response.Headers.Location;    //修改 HTTP PUT    myProduct.Price = 80;   // Update price    response = await client.PutAsJsonAsync(pUrl, myProduct);    //刪除 HTTP DELETE    response = await client.DeleteAsync(pUrl);}//異步獲取數據response = await client.GetAsync("/api/Product");if (response.IsSuccessStatusCode){    IEnumerable<Product> products = await response.Content.ReadAsAsync<IEnumerable<Product>>();    foreach (var item in products)    {Console.WriteLine("{0}\t{1}元\t{2}", item.Name, item.Price, item.Category);    }    }    }}

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