为什么找不到我的控制器？

Question

我开始通过创建Web API和客户端来使用Web Api，所有工作正常，直到我从GetAsync()切换到PostAsync()，现在每次都得到404响应，为什么会这样是？

服务器端代码

[HttpPost]
[Route("users/verifyLoginCredentials/{username}/{password}")]
public IHttpActionResult VerifyLoginCredentials(string username, string password)
{
            var verificationResult = Models.User.VerifyLoginCredentials(username, password);
            if (verificationResult)
            {
                return Ok("Login Successful");
            }

       return BadRequest("Login Failed");
}

.Net 4.5客户端代码

static async Task<Uri> verifyLoginCredentials(string username, string password)
{
   HttpClient client = new HttpClient();

    client.BaseAddress = new Uri("http://localhost:4685/");
    client.DefaultRequestHeaders.Accept.Clear();
    client.DefaultRequestHeaders.Accept.Add(
        new MediaTypeWithQualityHeaderValue("application/json"));

    var value = new Dictionary<string, string>
    {
       { "username", "hello" },
       { "password", "world" }
    };

    var content = new FormUrlEncodedContent(value);
    var result = await client.PostAsync("users/verifyLoginCredentials/", content);
    string resultContent = await result.Content.ReadAsStringAsync();


    result.EnsureSuccessStatusCode();

    // return URI of the created resource.
    return result.Headers.Location;
}