How does Entity Framework determine that a specific property of an object has been changed?

Entity Framework tracks changes to object properties using the Change Tracking mechanism. When an object is loaded from the database, EF saves its original state. When the SaveChanges() method is called, EF compares the current state of the object with the saved original state. If a property value has changed, EF marks that property as modified and generates the corresponding SQL update query.

For classes that implement the INotifyPropertyChanged interface, EF can track changes immediately as they occur. Otherwise, the comparison happens upon saving.

Example:

var user = context.Users.Find(1);
user.Name = "New Name"; // EF will mark the Name property as modified
context.SaveChanges(); // will update only the changed fields in the database