使用 WebClient 调用 Web API

因为老版本的 .NET 没有 HttpClient，所以只能使用 WebClient 或借助第三方包进行 Web API 的调用。

GET

using (var client = new WebClient())
{
    client.Headers[HttpRequestHeaders.Accept] = "application/json";
    string result = client.DownloadString("http://example.com/values");
    // now use a JSON parser to parse the resulting string back to some CLR object
    var todo = JsonConvert.DeserializeObject<Todo>(result);
}

PUT

string data = JsonConvert.SerializeObject(record);
try
{
    // 好像是因为官方 Headers 设置存在问题，所以没法把 Content-Type 和 Accept 放在一起初始化
    client.Headers["Content-Type"] = "application/json";
    client.UploadString("http://example.com/values", WebRequestMethods.Http.Put, data);
}
catch (WebException ex)
{
    Logger.Error(ex, $"PUT failed data: {data}");
    throw;
}

POST

using (var client = new WebClient())
{
    client.Headers[HttpRequestHeader.ContentType] = "application/json";
    client.Headers[HttpRequestHeader.Accept] = "application/json";
    var data = Encoding.UTF8.GetBytes("{\"foo\":\"bar\"}");
    byte[] result = client.UploadData("http://example.com/values", "POST", data);
    string resultContent = Encoding.UTF8.GetString(result, 0, result.Length);        
    // now use a JSON parser to parse the resulting string back to some CLR object 
    var content = JsonConvert.DeserializeObject<Content>(resultContent);
}

DELETE

public void DeleteRecord(string id)
{
    client.UploadValues($"https://example.com/api/records/{id}", "DELETE",
        new NameValueCollection());
}

参考

• Consume Web API Using WebClient In C#
• Calling Web Api service from a .NET 2.0 client