‫چند نکته کاربردی درباره Entity Framework

An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key

T attachedEntity = set.Find(entity.Id);
var attachedEntry = dbContext.Entry(attachedEntity);
attachedEntry.CurrentValues.SetValues(entity);

public DbContext()
        {
            this.Configuration.ProxyCreationEnabled = false;
            this.Configuration.LazyLoadingEnabled = false;
            this.Configuration.AutoDetectChangesEnabled = false;
         }

 dbContext.Entry(entity).State = EntityState.Detached;

// group id=19  Name="General"  
var customer = new Customer();
customer.Group = group;
customer.Name = "mohammadi";
dbContext.Entry(customer).State = EntityState.Added;
var customerstate = dbContext.Entry(customer).State;// customerstate=EntityState.Added
var groupstate = dbContext.Entry(group);// groupstate=EntityState.Added

// group id=19  Name="General"  
var customer = new Customer();
customer.Group = group;
 customer.Name = "mohammadi";
dbContext.Entry(group).State = EntityState.Unchanged;
dbContext.Entry(customer).State = EntityState.Added;
var customerstate = dbContext.Entry(customer).State;// customerstate=EntityState.Added
 var groupstate = dbContext.Entry(group);// groupstate=EntityState.Unchanged

  // group id=19  Name="General"  
var customer = new Customer();
 customer.Group = group;
customer.Name = "mohammadi";
dbContext.Entry(customer).State = EntityState.Unchanged;
dbContext.Entry(customer).State = EntityState.Added;
var customerstate = dbContext.Entry(customer).State;// customerstate=EntityState.Added
var groupstate = dbContext.Entry(group);//// groupstate=EntityState.Unchanged

var customer  = dbContext.Customers.FirstOrDefault();
 var customerAsNoTracking  = dbContext.Customers.AsNoTracking().FirstOrDefault();
var customerstate = dbContext.Entry(customer).State;// customerstate=EntityState.Unchanged
var customerstateAsNoTracking  = dbContext.Entry(customerAsNoTracking).State;// customerstate=EntityState.Detached

var Entries = dbContext.ChangeTracker.Entries();    
var AddedEntries = dbContext.ChangeTracker.Entries().Where(entityEntry => entityEntry.State==EntityState.Added);
var ModifiedEntries = dbContext.ChangeTracker.Entries().Where(entityEntry => entityEntry.State==EntityState.Modified);
var UnchangedEntries = dbContext.ChangeTracker.Entries().Where(entityEntry => entityEntry.State==EntityState.Unchanged);
var DeletedEntries = dbContext.ChangeTracker.Entries().Where(entityEntry => entityEntry.State==EntityState.Deleted);
var DetachedEntries = dbContext.ChangeTracker.Entries().Where(entityEntry => entityEntry.State==EntityState.Detached);//* not working !

 public virtual void AddOrUpdate(T entity)
        {
            if (entity.Id == 0)
                Add(entity);
            else
                Update(entity);

        }

 public class DataGridViewChildRelationTextBoxCell : DataGridViewTextBoxCell
    {
        protected override object GetValue(int rowIndex)
        {
            try
            {
                var bs = (BindingSource)DataGridView.DataSource;
                var cl = (DataGridViewChildRelationTextBoxColumn)DataGridView.Columns[ColumnIndex];
                return getChildValue(bs.List[rowIndex], cl.DataPropertyName).ToString();
            }
            catch (Exception)
            {
                return "";
            }
        }

        private object getChildValue(object dataSource, string childMember)
        {
            int nextPoint = childMember.IndexOf('.');
            if (nextPoint == -1) return dataSource.GetType().GetProperty(childMember).GetValue(dataSource, null);
            string proName = childMember.Substring(0, nextPoint);
            object newDs = dataSource.GetType().GetProperty(proName).GetValue(dataSource, null);
            return getChildValue(newDs, childMember.Substring(nextPoint + 1));
        }
    }

    public class DataGridViewChildRelationTextBoxColumn : DataGridViewTextBoxColumn
    {
        public string DataMember { get; set; }

        public DataGridViewChildRelationTextBoxColumn()
        {
            CellTemplate = new DataGridViewChildRelationTextBoxCell();
        }
    }

GroupNameColumn= new DataGridViewChildRelationTextBoxColumn(); //from your class
GroupNameColumn.HeaderText = "گروه مشتری";
GroupNameColumn.DataPropertyName = "Group.Name"; //EF  Property: Customer.Group.Name
GroupNameColumn.Visible = true;
GroupNameColumn.Width = 300;
DataGridView.Columns.Add(GroupNameColumn);