Columns Recompute

Let's review the columns collection and it's role in the Recompute

• Columns that are not added to the column collection will not participate in the recompute

BindValue will only recompute based on columns that were added before it in the Columns Collection

• Add a local column EndOfMonth

    public class DemoColumnsCollection : UIControllerBase
    {
        public readonly Models.Orders Orders = new Models.Orders();
        public readonly DateColumn EndOfMonth = new DateColumn("EndOfMonth");
        public DemoColumnsCollection()
        {
            From = Orders;

            Columns.Add(Orders.OrderID);
            Columns.Add(Orders.CustomerID);
            Columns.Add(Orders.OrderDate);
        }
        public void Run()
        {
            Execute();
        }
        protected override void OnLoad()
        {
            View = () => new Views.DemoColumnsCollectionView(this);
        }
    } 

• Add a BindValue for the EndOfMonth column

    public class DemoColumnsCollection : UIControllerBase
    {
        public readonly Models.Orders Orders = new Models.Orders();
        public readonly DateColumn EndOfMonth = new DateColumn("EndOfMonth");
        public DemoColumnsCollection()
        {
            From = Orders;

            Columns.Add(Orders.OrderID);
            Columns.Add(Orders.CustomerID);
            Columns.Add(Orders.OrderDate);
            Columns.Add(EndOfMonth).BindValue(() => Orders.OrderDate.EndOfMonth);
        }
        public void Run()
        {
            Execute();
        }
        protected override void OnLoad()
        {
            View = () => new Views.DemoColumnsCollectionView(this);
        }
    } 

• Note that in the migrated code, the call to BindValue will be attached to the Columns.Add call for that column
• Note that if the Columns.Add of the EndOfMonth column is after the call to Columns.Add of the Orders.OrderDate column, the value of EndOfMonth will automatically change whenever the value of Orders.OrderDate changes
• Note that if the Columns.Add of the EndOfMonth column is Before the call to Columns.Add of the Orders.OrderDate column, the value of EndOfMonth will NOT automatically change whenever the value of Orders.OrderDate changes, it'll only evaluate once when you enter the row.
• We can use Alt + up arrow to move a line of code up, or Alt + down arrow to move a line of code down

Debugging

• Break into the code using the Shift + F12
• In the "Watch" window, use the __RecomputePath property of any column, to see the columns that when changed, will cause this column to recompute
  
• You can also use the 'Make Object ID' right click option, to highlight columns (or any object) in the watch window and the columns collection, using the {$1} symbol.
  
  

• Exercise Columns Recompute

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