Logic for tracking entity framework property value changes in MVC - entity-framework

Question

I think I am missing something in my understanding of tracking property value changes in entity framework.
I have an application where i store service requests. Whenever a team value in changed in the service request record, I want to create a team history record in a related teamhistory entity.
I have created the app in MVC using the standard scaffolding for controllers and views.
In the (post)edit task in the controller, the standard logic generated has the following code
if (ModelState.IsValid)
{
db.Entry(serviceRequest).State = EntityState.Modified;
await db.SaveChangesAsync();
return RedirectToAction("Index");
}
return View(serviceRequest);
I have modified that to include the creating of the teamhistory record and an individualhistory record for individual assigned within team. The code for creating these related records work, BUT i want these records only created when the values on team or member(individual) change from what they were previously.
So far the conditions i have specified due not trigger this correctly because I havent gotten the condition right. Below is the current code:
//string teamorig = db.Entry(serviceRequest).Property(u => u.Team).OriginalValue.ToString();
//string teamcurr = db.Entry(serviceRequest).Property(u => u.Team).CurrentValue.ToString();
//if (teamorig != teamcurr)
var TeamIsModified = db.Entry(serviceRequest).Property(u => u.Team).IsModified;
if (TeamIsModified)
{
serviceRequest.TeamAssignmentHistories.Add(new TeamAssignmentHistory()
{
DateAssigned = DateTime.Now,
AssignedBy = User.Identity.Name,
ServiceRequest = serviceRequest.Id,
Team = serviceRequest.Team
});
}
//=========================================================================================
// if individual assigned has changed add individual history record========================
var IndividualIsModified = db.Entry(serviceRequest).Property(u => u.Member).IsModified;
if (IndividualIsModified)
{
serviceRequest.IndividualAssignmentHistories.Add(new IndividualAssignmentHistory()
{
DateAssigned = DateTime.Now,
AssignedBy = User.Identity.Name,
ServiceRequest = serviceRequest.Id,
AssignedTo = serviceRequest.Member.Value,
});
}
//===========================================================================================
The var teamismodified logic doesnt work. When I save the page without making any changes on it- the logic kicks off because in debugging it thinks the field has been modified.
When I comment out that code and uncomment the code above it for original and currentvalues- ie the teamorig and teamcurr logic, teamcurr and teamorig have the same values in debug, even when they have been forced into a change on the save in the MVC view page. Because they have the same values, the if condition is false so the team history record is not created.
The above code has been sandwiched in between
db.Entry(serviceRequest).State = EntityState.Modified;
and
await db.SaveChangesAsync();
statements.
What am I not understanding about entity framework tracking changes in mvc? Why does think its modified when i make not changes to team, and why are teamorig and teamcurr the same when I do make the changes?
Any advice would be welcome. Thanks