Question

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

对于这种类型的响应，我也无法创建其模型类。响应：

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，那么哪种方法会有所帮助以及如何使用。

我已经尝试过的代码：

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进行进一步处理，因此在继续进行操作之前，我必须需要此方法来完成其执行

Answer 1

首先从Json创建模型：

使用Json2C#之类的在线模型生成器，为您发布的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; }
}

现在使用WebAPI连接到HttpClient，它可以选择同时返回Json和CSV，我希望JSON被标准，也可以由各种客户端轻松使用，使用以下简单的通用方法：

假设它仅是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：

简单调用：

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

您会收到反序列化的RootObject，如上面的模型所示
对于任何进一步复杂的处理，例如将输入内容发送到带有http正文的调用，上述通用代码需要进一步修改，目前仅针对您的要求

编辑1 ：（使输入呼叫同步）

要使整个调用保持同步，请在最顶层使用GetAwaiter().GetResult()，Main方法将转换为，其余所有都将与示例中的相同（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

您可以使用诸如json2csharp之类的在线服务来获取json模型，并使用Json.Net来序列化和反序列化json字符串。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。

例如，要获取每个quotes的 bid，ask和midpoint 值，您只需执行以下操作：

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}");
}

在Winform C＃应用程序中从Web api调用并获取响应

2 个答案: