what is the best way to update in asp.net core
entity-framework-core
Question
I'm watching some tutorial programming about asp.net core
In some tutorial lecturers use this code for update data in database
DataContext db = new DataContext();
var query = db.TblUsers.where(x => x.Id == 3).single();
query.Name = "Sami";
db.TblUsers.Attach(query);
db.Entry(query).state = EntityState.Modified;
db.SaveChanges();
But some lecturers use this code for updating data in database
DataContext db = new DataContext();
var query = db.TblUsers.where(x => x.Id == 3).single();
query.Name = "Sami";
db.Update(query);
db.SaveChanges();
In fact I'm confuse to use which of them? Because both code working.
Please tell me what is exactly different between those codes ?
Accepted Answer
For your current code, there is no need to use Attach for the first way. If you want to update Model by retriving record from database, kindly go with second way which is much convenience.
For Attach, it will put entity in the graph into the Unchanged state, and set entity as Modified by db.Entry(query).state = EntityState.Modified, then the changes in query will be saved to database. Since db.TblUsers.where(x => x.Id == 3).single() is already tracking the query, there is no need to use Attach.
There are two types for query, tracking and no-tracking. If you did not specificy the query as no-tracking expecitly like db.TblUsers.AsNoTracking().where(x => x.Id == 3).single(), the entity will be tracking which is Unchanged state.
For db.Update(query);, it will begins tracking the given entity in the EntityState.Modified state such that it will be updated in the database when Microsoft.EntityFrameworkCore.DbContext.SaveChanges is called.
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