angularjs $http post object always null - angularjs

Question

I'm trying to send an object to the backend with an $http post, but one of the parameters is always null. I'm formatting the dto in the same way when saving a new object and that works fine, but when I try to call the update function it's not working. What am I missing?
This is my controller code:
vm.postUpdateITSM = function (itsm) {
$http({
method: "POST",
url: "api/sources/" + itsm.Id,
data: {
id: itsm.Id,
dto: {
ConnectorType: itsm.Type,
SourceName: itsm.ServerName,
DisplayName: itsm.DisplayName,
Credentials: JSON.stringify(itsm.UserName,
itsm.Password),
Url: itsm.URL,
Settings: JSON.stringify(itsm.ResolveAlerts ? itsm.ResolveAlerts : false,
itsm.AcknowledgeAlerts ? itsm.AcknowledgeAlerts : false,
itsm.SyncInterval,
itsm.IncidentInterval,
itsm.Status ? itsm.Status : "")
}
}
});
}
And on the back end: The dto is always null when called.
public async Task<IHttpActionResult> Update(int id, [FromBody] SourceDto dto)
{
var source = Mapper.Map<Source>(dto);
source.SourceID = id;
source.ServerCount = "";
var res = await SystemActors.SourceManager.Ask(new UpdateSource(source));
var failure = res as Status.Failure;
if (failure != null)
{
return InternalServerError();
}
var success = ((SqlResult<object>) res).Success;
if (!success)
{
return Content(HttpStatusCode.BadRequest, "Failed to update source.");
}
return Ok(new ResponsePackage {Success = true});
}
And this is the SourceDto class:
public class SourceDto
{
public string ConnectorType { get; set; }
public string SourceName { get; set; }
public string DisplayName { get; set; }
public string Credentials { get; set; }
public string Url { get; set; }
public string Settings { get; set; }
}

Answer 1

Your frontend data is formatted a bit wrong - the data parameter should just be the one object your ASP.NET controller is expecting in the [FromBody], your SourceDto model - and the id should be a query string:
method: "POST",
url: "api/sources/" + itsm.Id,
data: {
ConnectorType: itsm.Type,
SourceName: itsm.ServerName,
DisplayName: itsm.DisplayName,
Credentials: JSON.stringify(itsm.UserName,
itsm.Password),
Url: itsm.URL,
Settings: JSON.stringify(itsm.ResolveAlerts ? itsm.ResolveAlerts : false,
itsm.AcknowledgeAlerts ? itsm.AcknowledgeAlerts : false,
itsm.SyncInterval,
itsm.IncidentInterval,
itsm.Status ? itsm.Status : "")
}
});
ASP.NET will apply the request body to the expected model - if it doesn't match, you'll get null