Ajax提交json字符串给后台处理

function save() {
var imgStr = getImgStr();
var positionObj = getPositionObj();

if (positionObj != null) {
var paramObj = getParamObj();
var userObj = getUserObj();

if (paramObj != null) {
var obj = { "positionObj": positionObj, "paramObj": paramObj, "userObj": userObj, "imgStr": imgStr };
$.ajax({
type: "post",
url: "/Company/Project/ProcessAdd",
contentType: "application/json; charset=utf-8",
data: JSON.stringify(obj),
dataType: "json",
success: function (message) {
if (message > 0) {
alert("请求已提交！我们会尽快与您取得联系");
}
},
error: function (message) {
alert("提交数据失败！");
}
});
}
}
}

public ActionResult ProcessAdd()
{

var sr = new StreamReader(Request.InputStream);
var str = sr.ReadToEnd();

var json = DynamicJson.Parse(str);

//.....处理业务

//返回 跳转
return null;
}