问张贴到Web参数为空

EN

$.post("/api/amazon/signature", { "policy": policy }, function (data) {
    console.log(data);
});

// POST api/amazon/signature
[HttpPost]
[Route("api/amazon/signature")]
public IHttpActionResult GetSignature([FromBody]string policy)
{
    var bKey = Encoding.ASCII.GetBytes(ConfigurationManager.AppSettings["AWSSecretKey"]);
    var hmacSha1 = new HMACSHA1(bKey);

    var bPolicy = Encoding.ASCII.GetBytes(policy);
    var hash = hmacSha1.ComputeHash(bPolicy);
    var encoded = Convert.ToBase64String(hash);

    return Ok(encoded);
}

public class Signature
{
    public string Policy { get; set; }
}

// POST api/amazon/signature
[HttpPost]
[Route("api/amazon/signature")]
public IHttpActionResult GetSignature([FromBody]Signature model)
{
    var bKey = Encoding.ASCII.GetBytes(ConfigurationManager.AppSettings["AWSSecretKey"]);
    var hmacSha1 = new HMACSHA1(bKey);

    var bPolicy = Encoding.ASCII.GetBytes(model.Policy);
    var hash = hmacSha1.ComputeHash(bPolicy);
    var encoded = Convert.ToBase64String(hash);

    return Ok(encoded);
}

$.post("/api/amazon/signature", { "Policy": policy }, function (data) {
    console.log(data);
});