無法在控制檯應用程序中使用GET方法

Question

我創建了一個web API，其中CRUD操作執行。現在我想實時測試它，所以我決定通過遵循this教程來製作控制檯應用程序。本教程提供了在運行應用程序時自己創建產品並獲取，更新和刪除它的代碼的代碼。但我想使用用戶輸入。我成功地創造了產品。不過，雖然得到它我面臨的一個問題，看我的代碼

類

class Product 
{   

    [Key] 
    public string Id { get; set; } 

    [Required] 
    public string Name { get; set; } 

    [Required] 
    public decimal Price { get; set; } 

    [Required] 
    public string Category { get; set; } 
} 

控制檯

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; 

     client.BaseAddress = new Uri("http://localhost:7361/"); 
     client.DefaultRequestHeaders.Accept.Clear(); 
     client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json")); 

     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 }; 

        var 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: 

        Environment.Exit(0); 

        break; 
      } 
} 

在case 2在product = await GetProductAsync(url.PathAndQuery);，我無法使用url變量它說Use of unassigned local variable 'url'。

另外我不能聲明var外面，因爲它不會被初始化爲任何人。

我試圖將類型從var更改爲string但仍無法執行任務。

任何幫助將高度讚賞

Answer 1

與我們分享您對如何賄賂編譯器允許使用未賦值的變量的提示;）

你試圖內case 2:雖然該變量沒有按使用可變url在這種情況下存在't。看來你已經宣佈url內case 1:，技術上這個變量不能是過去break聲明結束的情況下訪問1.

回去了一步，對variable scope within switch statement in c#

快速閱讀速戰速決是delcare Uri url就在switch()之前，所以在交換機的所有情況下都可以訪問。只要確保你給它一個初始值或者添加一個default:語句並在之前將它初始化，然後在代碼中進一步使用它。