如何在VB.NET中实现调用CoinGecko API的指定Curl请求？

原Curl请求对应需求 #

你需要实现的Curl请求是获取比特币的USD价格，参数已指定不需要额外扩展数据，请求格式为JSON：

curl -X 'GET' \
'https://api.coingecko.com/api/v3/simple/price?ids=bitcoin&vs_currencies=usd&include_market_cap=false&include_24hr_vol=false&include_24hr_change=false&include_last_updated_at=false&precision=full' \
-H 'accept: application/json'

以下是两种可行的VB.NET实现方式：

方法1：使用HttpClient（推荐，适用于.NET Core/.NET 5+及新版.NET Framework） #

HttpClient是.NET官方推荐的现代HTTP客户端，支持异步操作，性能更优且资源占用合理。

完整示例代码 #

Imports System.Net.Http
Imports System.Text.Json

Module CoinGeckoApiExample
    ' 全局单例HttpClient，避免重复创建导致端口耗尽
    Private ReadOnly _httpClient As New HttpClient()

    Async Function GetBitcoinPriceAsync() As Task(Of Decimal?)
        Try
            ' 构造请求URL
            Dim requestUrl As String = "https://api.coingecko.com/api/v3/simple/price?ids=bitcoin&vs_currencies=usd&include_market_cap=false&include_24hr_vol=false&include_24hr_change=false&include_last_updated_at=false&precision=full"
            
            ' 设置请求头
            _httpClient.DefaultRequestHeaders.Accept.Clear()
            _httpClient.DefaultRequestHeaders.Accept.Add(New System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"))

            ' 发送GET请求并获取响应
            Dim response As HttpResponseMessage = Await _httpClient.GetAsync(requestUrl)
            response.EnsureSuccessStatusCode() ' 抛出HTTP错误状态码异常

            ' 读取并解析JSON响应
            Dim jsonResponse As String = Await response.Content.ReadAsStringAsync()
            Dim priceData As Dictionary(Of String, Dictionary(Of String, Decimal)) = JsonSerializer.Deserialize(Of Dictionary(Of String, Dictionary(Of String, Decimal)))(jsonResponse)

            ' 提取比特币USD价格
            Return priceData("bitcoin")("usd")
        Catch ex As HttpRequestException
            Console.WriteLine($"请求出错：{ex.Message}")
            Return Nothing
        Catch ex As KeyNotFoundException
            Console.WriteLine("API返回数据格式异常")
            Return Nothing
        End Try
    End Function

    ' 调用示例（需在异步上下文执行）
    Async Sub Main()
        Dim price As Decimal? = Await GetBitcoinPriceAsync()
        If price.HasValue Then
            Console.WriteLine($"当前比特币价格：${price.Value:N2}")
        Else
            Console.WriteLine("无法获取比特币价格")
        End If
    End Sub
End Module

补充说明 #

• HttpClient必须全局单例使用，禁止每次请求时创建新实例，否则会导致系统端口耗尽。
• 若使用.NET Framework，需确保项目引用了System.Net.Http程序集。
• 若偏好使用Newtonsoft.Json（Json.NET）解析JSON，可替换反序列化代码：

  Imports Newtonsoft.Json
  ' ...
  Dim priceData As Dictionary(Of String, Dictionary(Of String, Decimal)) = JsonConvert.DeserializeObject(Of Dictionary(Of String, Dictionary(Of String, Decimal)))(jsonResponse)
  

方法2：使用WebClient（适用于旧版.NET Framework） #

WebClient是较旧的HTTP客户端，API简单但功能有限，不推荐在新项目中使用。

示例代码 #

Imports System.Net
Imports Newtonsoft.Json ' 需要引用Newtonsoft.Json NuGet包

Module CoinGeckoWebClientExample
    Function GetBitcoinPrice() As Decimal?
        Try
            Dim requestUrl As String = "https://api.coingecko.com/api/v3/simple/price?ids=bitcoin&vs_currencies=usd&include_market_cap=false&include_24hr_vol=false&include_24hr_change=false&include_last_updated_at=false&precision=full"
            
            Using webClient As New WebClient()
                webClient.Headers.Add(HttpRequestHeader.Accept, "application/json")
                Dim jsonResponse As String = webClient.DownloadString(requestUrl)
                
                Dim priceData As Dictionary(Of String, Dictionary(Of String, Decimal)) = JsonConvert.DeserializeObject(Of Dictionary(Of String, Dictionary(Of String, Decimal)))(jsonResponse)
                Return priceData("bitcoin")("usd")
            End Using
        Catch ex As WebException
            Console.WriteLine($"请求出错：{ex.Message}")
            Return Nothing
        Catch ex As KeyNotFoundException
            Console.WriteLine("API返回数据格式异常")
            Return Nothing
        End Try
    End Function

    Sub Main()
        Dim price As Decimal? = GetBitcoinPrice()
        If price.HasValue Then
            Console.WriteLine($"当前比特币价格：${price.Value:N2}")
        Else
            Console.WriteLine("无法获取比特币价格")
        End If
    End Sub
End Module

内容的提问来源于stack exchange，提问作者John Paul Attard