WEBAPI中的Request是HttpRequestMessage类型，不能像Web传统那样有querystring和from 方法接收参数，而传统的HttpReqest的基类是HttpReqestBase
所以这里我们就直接使用(HttpContextBase)Request.Properties["MS_HttpContext"]
public void Post([FromBody]string value)
{
HttpContextBase context = (HttpContextBase)Request.Properties["MS_HttpContext"];//获取传统context
HttpRequestBase request = context.Request;//定义传统request对象
string name = request.Form["name"];
}