Additional Events for Data Related Debugging

Sometimes you want to track down an update to a specific entity or a specific column. You can do that by overriding the OnSavingRow Entity method or by handle the ValueChange event of a column.

overriding the OnSavingRow method of an entity

As of version 30735 a new method was added to entity called OnSavingRow The OnSavingRow event of entities is called after the Controller's OnSavingRow and before the entity is saved to the database. You can put all sorts of logic in such methods and you can also use it for debugging purposes. For example:

public class Orders : Entity
{
    #region Columns
    ...
    #endregion
    public Orders() : base("dbo.Orders", "Orders", Northwind.Shared.DataSources.Northwind1)
    {
        Cached = false;
        InitializeIndexes();
    }
    protected override void OnSavingRow(IEntityOnSavingRowEventArgs e)
    {
        if (e.Activity == Activities.Update && this.OrderDate.WasChanged)
        {
            System.Diagnostics.Debug.WriteLine("Order Date was Changed from:" + OrderDate.OriginalValue + " to: " + OrderDate.Value);
        }
        base.OnSavingRow(e);
    } 

Handling the ValueChange event of a column

Sometimes if you want to see what code exactly updates a column, simply handle it's ValueChanged event and add a breakpoint in it. For example the following code will write to the output whenever the OrderDate is actually changed (way before it's saved to the database)

public Orders() : base("dbo.Orders", "Orders", Northwind.Shared.DataSources.Northwind1)
{
    Cached = false;
    InitializeIndexes();
    OrderDate.ValueChanged += e =>
    {
        System.Diagnostics.Debug.WriteLine("OrderDate was changed from " + e.PreviousValue + " to " + OrderDate.Value);
    };
} 

Finding when the row was changed

When the OnSavingRow() method is triggered, it means that the the row was changed. In some cases, specially in large programs, you sometimes do not know where the change of the record came from. The RowChanging event, which can be declared in the controller, can assist you with that.

public ShowOrders()
 {
    Title = "ShowOrders";
    InitializeDataViewAndUserFlow();
    InitializeHandlers();
    RowChanging += () =>
    {
       MessageBox.Show("Row was changed");
    };
} 

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