使用HttpClient增删改查ASP.NET Web API服务

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2023-06-01
C# WinForm实现自动更新程序的方法详解
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标签   ASP.NET

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);
            }
            
        }
    }
}

C# WinForm实现自动更新程序的方法详解
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