本篇体验使用HttpClient对ASP.NET Web API服务实现增删改查。

创建ASP.NET Web API项目

新建项目,选择"ASP.NET MVC 4 Web应用程序"。

选择"Web API"。

在Models文件夹下创建Product类。

    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文件夹下创建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文件夹下创建ProductRepository类,实现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文件夹下创建空的ProductController。

   public class ProductController : ApiController
    {
        static readonly IProductRepository repository = new ProductRepository();
        //获取所有
        public IEnumerable<Product> GetAllProducts()
        {
            return repository.GetAll();
        }
        //根据id获取
        public Product GetProduct(int id)
        {
            Product item = repository.Get(id);
            if (item == null)
            {
                throw new HttpResponseException(HttpStatusCode.NotFound);
            }
            return item;
        }
        //根据类别查找所有产品
        public IEnumerable<Product> GetProductsByCategory(string category)
        {
            return
                repository.GetAll().Where(p => string.Equals(p.Category, category, StringComparison.OrdinalIgnoreCase));
        }
        //创建产品
        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;
        }
        //更新产品
        public void PutProduct(int id, Product product)
        {
            product.Id = id;
            if (!repository.update(product))
            {
                throw new HttpResponseException(HttpStatusCode.NotFound);
            }
        }
        //删除产品
        public void DeleteProduct(int id)
        {
            Product item = repository.Get(id);
            if (item == null)
            {
                throw new HttpResponseException(HttpStatusCode.NotFound);
            }
            repository.Remove(id);
        }
    }

在浏览器中输入:

http://localhost:1310/api/Product   获取到所有产品
http://localhost:1310/api/Product/1   获取编号为1的产品

使用HttpClient查询某个产品

在同一个解决方案下创建一个控制台程序。

依次点击"工具","库程序包管理器","程序包管理器控制台",输入如下:

Install-Package Microsoft.AspNet.WebApi.Client

在控制台程序下添加Product类,与ASP.NET Web API中的对应。

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

编写如下:

        static void Main(string[] args)
        {
            RunAsync().Wait();
            Console.ReadKey();
        }
        static async Task RunAsync()
        {
            using (var client = new HttpClient())
            {
                //设置
                client.BaseAddress = new Uri("http://localhost:1310/");
                client.DefaultRequestHeaders.Accept.Clear();
                client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
                //异步获取数据
                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);
                }
            }
        }

把控制台项目设置为启动项目。

HttpResponseMessage的IsSuccessStatusCode只能返回true或false,如果想让响应抛出异常,需要使用EnsureSuccessStatusCode方法。

try
{
    HttpResponseMessage response = await client.GetAsync("/api/Product/1");
    response.EnsureSuccessStatusCode();//此方法确保响应失败抛出异常
}
catch(HttpRequestException ex)
{
    //处理异常
}

另外,ReadAsAsync方法,默认接收MediaTypeFormatter类型的参数,支持 JSON, XML, 和Form-url-encoded格式,如果想自定义MediaTypeFormatter格式,参照如下:

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

使用HttpClient查询所有产品

       static void Main(string[] args)
        {
            RunAsync().Wait();
            Console.ReadKey();
        }
        static async Task RunAsync()
        {
            using (var client = new HttpClient())
            {
                //设置
                client.BaseAddress = new Uri("http://localhost:1310/");
                client.DefaultRequestHeaders.Accept.Clear();
                client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
                //异步获取数据
                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())
            {
                //设置
                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);
                //异步获取数据
                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())
            {
                //设置
                client.BaseAddress = new Uri("http://localhost:1310/");
                client.DefaultRequestHeaders.Accept.Clear();
                client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
                //添加 HTTP POST
                var 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);
                }
                //异步获取数据
                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删除

        static void Main(string[] args)
        {
            RunAsync().Wait();
            Console.ReadKey();
        }
        static async Task RunAsync()
        {
            using (var client = new HttpClient())
            {
                //设置
                client.BaseAddress = new Uri("http://localhost:1310/");
                client.DefaultRequestHeaders.Accept.Clear();
                client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
                //添加 HTTP POST
                var 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);
                    //删除 HTTP delete
                    response = await client.DeleteAsync(pUrl);
                }
                //异步获取数据
                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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