在 Visual Basic 中实现 HTTP 请求需要使用 System.Net 命名空间中的 HttpClient 类。以下是示例代码，其中包括如何发送 GET 和 POST 请求，同时设置请求头和请求体：
发送 GET 请求：
Dim url As String = "http://example.com/api/data"
Dim client As New HttpClient()
Dim response As HttpResponseMessage = Await client.GetAsync(url)
Dim content As String = Await response.Content.ReadAsStringAsync()
发送 POST 请求：
Dim url As String = "http://example.com/api/data"
Dim client As New HttpClient()
Dim requestBody As New StringContent("data=value")
requestBody.Headers.ContentType = New MediaTypeHeaderValue("application/x-www-form-urlencoded")
Dim response As HttpResponseMessage = Await client.PostAsync(url, requestBody)
Dim content As String = Await response.Content.ReadAsStringAsync()
以上代码仅供参考，具体实现需要根据实际需求进行调整。