Question

我在1和2教程之后创建了web-API个产品。第二个教程是调用web-api的控制台应用程序。现在，当我创建单个产品时，它可以查看。但是当我创建多个产品时，只有最后一个条目才能查看。为了更好地理解，请参阅以下代码。

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:...
       }

我想查看所有创建的产品。为此，我必须在创建产品时创建产品列表。但问题是我不知道该怎么办？

更新1

在调试代码时，static async Task<Product> GetProductAsync(string path) path将最后一个产品ID称为'api / product / 2'，但我希望像'api / product /'。该路径包含最后输入的id。

更新2

要获取我在url

中输入product = await GetProductAsync("http://localhost:7361/api/product");的所有产品

但是现在运行应用程序后，我收到以下错误。

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

更新3

通过检查Postman中的API响应，以下是我得到的数据

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

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Answer 1

从API返回的JSON（返回所有产品）表示对象集合，但在您的代码中，您尝试将其反序列化为单个产品对象。

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

以下是您需要进行的更改，以使您的代码正常运行。创建一个新方法，该方法将调用GetAllProducts API并返回产品集合，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;
}

我建议创建新方法，因为您可能在其他地方使用旧方法。现在，在switch case 2中使用以下新方法：

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);
    }

这可以帮助您解决问题。

使用控制台应用程序从WEB API获取所有数据

1 个答案: