How to update already tracked entity - entity-framework

Question

Hello i have the following problem:
I am retrieving an entity using EF Core and then inside a transaction i try to update it.
The update throws exception if i try to change the entity state to MODIFIED AFTER i retrieve it from the database.
I understood later on that if i get the entity from the context, it is already tracked at that point, and all further updates do not need to imply changing the entity state.
Based on this assumption in the code below i have commented the state change.Unfortunately at the end the entity does not get updated.Even if i call SaveChanges.
public void SomeMethod(DbContext context)
{
var entity=this.context.Find([some entity]); // the entity is started to get tracked
using(var tran=this.context.BeginTransaction())
{
try
{
//do some modifications on entity
// entity.Field1="tt";
// entity.Field2="ttx";
//this.context(entity).State=State.Modified -> throws exception saying entity is already tracked
this.context.SaveChanges();
tran.Commit(); // entity is not updated in the database !
}catch
{
tran.Rollback();
}
}
}
P.S Besides this i have also tried to first change the entity state to Detached and then Modified.It still threw exception on the Modified line.
Could someone tell me how to perform an update on an already tracked entity?
Update
I have also tried without transaction, and still the tracked entity does not get changed.So this basically does not save changes:
var entity=this.context.Find([some entity]);
//do some changes on entity without changing the entity state
this.context.SaveChanges();
Update 2
Apparently the problem is from the updates.I am not just setting fields.
I am indeed somewhere creating a new entity.

Answer 1

The problem was due to the fact that i was instantiating a new entity in my code and this new entity was not tracked and ... i was expecting it the pop up in the database.
Once i changed to an entity that was being tracked , the update was succesful without requiring to change its state to Modified or otherwise.