使用控制檯應用程序從WEB API獲取所有數據

Question

我已經在1和2教程中創建了產品web-API。第二個教程是調用web-api的控制檯應用程序。現在，當我創建一個單一的產品，然後它是查看能力。但是，當我創建不止一種產品時，只有最後一個條目才能被查看。爲了更好的理解，請看下面的代碼。

static HttpClient client = new HttpClient(); 

    static void ShowProduct(Product product) 
    { 

     Console.WriteLine($"Name: {product.Name}\tPrice: {product.Price}\tCategory: {product.Category}"); 
    } 

    static async Task<Uri> CreateProductAsync(Product product) 
    { 
     HttpResponseMessage response = await client.PostAsJsonAsync("api/product/", product); 
     response.EnsureSuccessStatusCode(); 

     // return URI of the created resource. 
     return response.Headers.Location; 
    } 

    static async Task<Product> GetProductAsync(string path) 
    { 
     Product product = null; 
     HttpResponseMessage response = await client.GetAsync(path); 
     if (response.IsSuccessStatusCode) 
     { 
      product = await response.Content.ReadAsAsync<Product>(); 
     } 
     return product; 
    } 
static async Task RunAsync() 
    { 
     int a; 
     decimal price = 0; 
     string name = null, category = null; 
     char option; 
     //string url; 
     client.BaseAddress = new Uri("http://localhost:7361/"); 
     client.DefaultRequestHeaders.Accept.Clear(); 
     client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json")); 
     Uri url = null; 

     try 
     { 
      label: 
      Console.Write("1. Create a product\n"); 
      Console.Write("2. View products\n"); 
      Console.Write("3. Update a product\n"); 
      Console.Write("4. Delete a product\n"); 
      Console.Write("5. Exit\n"); 

      Console.WriteLine("\nEnter your choice: "); 
      a = Convert.ToInt32(Console.ReadLine()); 


      switch(a) 
      { 
       case 1: 

        Console.WriteLine("Enter name of the product: "); 
        name = Convert.ToString(Console.ReadLine()); 

        Console.WriteLine("\nEnter price of the product: "); 
        price = Convert.ToDecimal(Console.ReadLine()); 
        Console.WriteLine("\nEnter category of the product: "); 
        category = Convert.ToString(Console.ReadLine()); 

        // Create a new product 
        Product product = new Product { Name = name, Price = price, Category = category }; 

        url = await CreateProductAsync(product); 
        Console.WriteLine($"Created at {url}"); 

        Console.WriteLine("Want to create more product(s)? (y/n): "); 
        option = Convert.ToChar(Console.ReadLine()); 

        if(option == 'y' || option == 'Y') 
        { 
         Console.Clear(); 
         goto case 1; 
        } 
        else if(option == 'n' || option == 'N') 
        { 
         Console.Clear(); 
         goto label; 
        } 

        break; 

       case 2: 

        // Get the product 
        product = await GetProductAsync(url.PathAndQuery); 

        ShowProduct(product); 

        break; 
        //case 3:... 
        //case 4:... 
        //case 5:... 
     } 

我想查看所有創建的產品。爲此，我必須在創建產品時創建產品列表。但問題是我不知道該在哪裏做？

更新1

在調試代碼的static async Task<Product> GetProductAsync(string path)的path得到最後一個產品ID爲 'API /產品/ 2'，但我想是這樣的 'API /產品/'。路徑包括最後輸入的id。

更新2

爲了讓所有的產品我在product = await GetProductAsync("http://localhost:7361/api/product");

進入url但現在運行的應用程序後，我得到下面的錯誤。

Cannot deserialize the current JSON object (e.g. {「name」:「value」}) 

更新3

通過檢查Postman以下API響應是我得到

[ 
{ 
    "Id": 1, 
    "Name": "yo-yo", 
    "Category": "toys", 
    "Price": 45 
}, 
{ 
    "Id": 2, 
    "Name": "mobile", 
    "Category": "electronics", 
    "Price": 45000 
}] 

任何幫助將高度讚賞

Answer 1

的JSON從返回的數據API（返回所有產品）表示對象的集合，但在代碼中您是tryi將其反序列化爲單個產品對象。

product = await response.Content.ReadAsAsync<Product>(); 

以下是爲使代碼正常工作而需要做的更改。 創建一個將調用GetAllProducts API並返回產品集合的新方法，如下所示。

static async Task<List<Product>> GetAllProductsAsync(string path) 
{ 
    List<Product> products = null; 
    HttpResponseMessage response = await client.GetAsync(path); 
    if (response.IsSuccessStatusCode) 
    { 
     products = await response.Content.ReadAsAsync<List<Product>>(); 
    } 
    return products; 
} 

我建議創建新方法，因爲您可能在其他地方使用舊的方法。 現在，使用新的方法，在開關的情況下2如下：

case 2: 
    // Get all the products 
    var products = await GetAllProductsAsync(url.PathAndQuery); 

    // Loop thru the products and call ShowProduct method for each product in the list. 
    foreach(var product in products) 
    { 
     ShowProduct(product); 
    } 

這應該可以幫助您解決問題。