在 winform c# 应用程序中调用并从 web api 获取响应

Question

我正在 Windows 中制作一个简单的 WinForm 应用程序，我想获取一些有关外汇汇率的数据。所以我决定从 Oanda 调用一个 API。我尝试了几件事，但没有任何效果。它以 CSV 和 JSON 格式给出响应。我不知道哪个会更容易处理。

同样对于这种类型的响应，我无法创建它的模型类。 回应：

JSON：

{
  "meta": {
    "effective_params": {
      "data_set": "OANDA",
      "base_currencies": [
        "EUR"
      ],
      "quote_currencies": [
        "USD"
      ]
    },
    "endpoint": "spot",
    "request_time": "2019-06-08T12:05:23+00:00",
    "skipped_currency_pairs": []
  },
  "quotes": [
    {
      "base_currency": "EUR",
      "quote_currency": "USD",
      "bid": "1.13287",
      "ask": "1.13384",
      "midpoint": "1.13336"
    }
  ]
}

CSV：

base_currency,quote_currency,bid,ask,midpoint
EUR,USD,1.13287,1.13384,1.13336

我只需要这三个数字，哪种方法会有所帮助以及如何。

这段代码我已经试过了：

var client = new HttpClient();
client.BaseAddress = new Uri("https://www1.oanda.com/rates/api/v2/rates/");
HttpResponseMessage response = await client.GetAsync("spot.csv?api_key=<myapikey>&base=EUR&quote=USD");
string result = await response.Content.ReadAsStringAsync();
textBox1.Text = result;

编辑：我需要此调用的结果以进行进一步处理，因此我必须需要此方法来完成其执行，然后再继续进行

Answer 1

首先从 Json 创建模型：

1. 使用Json2C#之类的在线模型生成器，对于您发布的Json，生成的模型如下：

   public class EffectiveParams
   {
     public string data_set { get; set; }
     public List<string> base_currencies { get; set; }
     public List<string> quote_currencies { get; set; }
   }
   
   public class Meta
   {
     public EffectiveParams effective_params { get; set; }
     public string endpoint { get; set; }
     public DateTime request_time { get; set; }
     public List<object> skipped_currency_pairs { get; set; }
   }
   
   public class Quote
   {
     public string base_currency { get; set; }
     public string quote_currency { get; set; }
     public string bid { get; set; }
     public string ask { get; set; }
     public string midpoint { get; set; }
   }
   
   public class RootObject
   {
     public Meta meta { get; set; }
     public List<Quote> quotes { get; set; }
   }
   

1234563的客户，请使用以下简单的通用方法：

假设它只是 GET 调用，只需将 Host 和 API 详细信息提供给下面的通用 Process 方法：

public async Task<TResponse> Process<TResponse>(string host,string api)
{
   // Execute Api call Async
   var httpResponseMessage = await MakeApiCall(host,api);

   // Process Json string result to fetch final deserialized model
   return await FetchResult<TResponse>(httpResponseMessage);
} 

public async Task<HttpResponseMessage> MakeApiCall(string host,string api)

{   
    // Create HttpClient
    var client = new HttpClient(new HttpClientHandler { UseDefaultCredentials = true }) { BaseAddress = new Uri(host) };
    client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

    // Make an API call and receive HttpResponseMessage
    HttpResponseMessage responseMessage = await client.GetAsync(api, HttpCompletionOption.ResponseContentRead);

    return responseMessage;
}

public async Task<T> FetchResult<T>(HttpResponseMessage result)
{
    if (result.IsSuccessStatusCode)
    {
        // Convert the HttpResponseMessage to string
        var resultArray = await result.Content.ReadAsStringAsync();

        // Json.Net Deserialization
        var final = JsonConvert.DeserializeObject<T>(resultArray);

        return final;
    }
    return default(T);
}

使用方法：

• 只需调用：

  var rootObj = await Process<RootObject>("https://www1.oanda.com/rates/", "api/v2/rates/");
  

• 您收到反序列化的RootObject，如上图所示

• 对于任何进一步复杂的处理，例如使用 http 正文向调用发送输入，以上通用代码需要进一步修改，目前仅针对您的要求

编辑 1：（使条目调用同步）

• 要使整体调用同步，请在最顶层使用GetAwaiter().GetResult()，Main 方法将被转换为，其余的将保持与示例中的相同（异步方法）

    void Main()
    {
       var rootObj =  Process<RootObject>("https://www1.oanda.com/rates/", "api/v2/rates/").GetAwaiter().GetResult();
    }
  

编辑 2：（使完整的代码同步）

void Main()
{
    var rootObj = Process<RootObject>("https://www1.oanda.com/rates/", "api/v2/rates/");
}


public TResponse Process<TResponse>(string host, string api)
{
    // Execute Api call
    var httpResponseMessage = MakeApiCall(host, api);

    // Process Json string result to fetch final deserialized model
    return FetchResult<TResponse>(httpResponseMessage);
}

public HttpResponseMessage MakeApiCall(string host, string api)

{
    // Create HttpClient
    var client = new HttpClient(new HttpClientHandler { UseDefaultCredentials = true }) { BaseAddress = new Uri(host) };
    client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

    // Make an API call and receive HttpResponseMessage
    HttpResponseMessage responseMessage = client.GetAsync(api, HttpCompletionOption.ResponseContentRead).GetAwaiter().GetResult();

    return responseMessage;
}

public T FetchResult<T>(HttpResponseMessage result)
{
    if (result.IsSuccessStatusCode)
    {
        // Convert the HttpResponseMessage to string
        var resultArray = result.Content.ReadAsStringAsync().GetAwaiter().GetResult();

        // Json.Net Deserialization
        var final = JsonConvert.DeserializeObject<T>(resultArray);

        return final;
    }
    return default(T);
}

Answer 2

您可以使用json2csharp 等在线服务获取您的json 模型，并使用Json.Net 对json 字符串进行序列化和反序列化。以下为您的 json 建模。

public class EffectiveParams
{
    public string data_set { get; set; }
    public List<string> base_currencies { get; set; }
    public List<string> quote_currencies { get; set; }
}

public class Meta
{
    public EffectiveParams effective_params { get; set; }
    public string endpoint { get; set; }
    public DateTime request_time { get; set; }
    public List<object> skipped_currency_pairs { get; set; }
}

public class Quote
{
    public string base_currency { get; set; }
    public string quote_currency { get; set; }
    public string bid { get; set; }
    public string ask { get; set; }
    public string midpoint { get; set; }
}

public class RootObject
{
    public Meta meta { get; set; }
    public List<Quote> quotes { get; set; }
}

请注意，您可以将RootOject 更改为更具描述性的名称。

因此，例如，要获得每个quotes 的出价、要价和中点值，您可以简单地执行以下操作：

RootObject rootObj=JsonConvert.DeserializeObject(jsonString);

//Get the required values.
foreach(var quote in rootObj.quotes)
{
Console.WriteLine($"Bid : {quote.bid} Ask: {quote.ask} MidPoint: {quote.midpoint}");
}