public static Task <HttpResponseMessage> PostFromJsonAsync <TValue>(this HttpClient client, string url, TValue value)
{
var json = JsonConvert.SerializeObject(value);
var content = new StringContent(json);
// 请求标题头
// Accept:*/*
client.DefaultRequestHeaders.Add("Accept", "*/*");
// Content-MD5: Base64(MD5(Body))
content.Headers.ContentMD5 = MD5Encrypt.GetContentMD5Data(json);
// Content-Type:application/json
content.Headers.ContentType = MediaTypeHeaderValue.Parse("application/json");
// Date:yyyy-MM-dd HH:mm:ss
//client.DefaultRequestHeaders.Add("Date", DateTime.Now.ToString());
// X-Ca-Key:密钥ID
client.DefaultRequestHeaders.Add("X-Ca-Key", "");
// X-Ca-Signature:签名
client.DefaultRequestHeaders.Add("X-Ca-Signature", Sha256.GetSignature(SecretKey, GetPresignature(client, content)));
// X-Ca-Signature-Headers:x-ca-key
client.DefaultRequestHeaders.Add("X-Ca-Signature-Headers", "x-ca-key");
return(client.PostAsync(url, content));
}