Programmatically databind Itemssource

[Mark]

I'm currently binding a GridView to its ItemSource with XAML as:

ItemsSource="{Binding Path=CurrentItem.tblPOLines, Mode=TwoWay, ElementName=df_POLedger}"

How can achieve this programmatically?

The "tblPOLines" is a child.  If it were the parent, it would be:

dg_tblPOLines.ItemsSource = df_POLedger.CurrentItem;

but I'm trying to go to the children.

Thanks,
Mark

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EDIT
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This was requested in trying to resolve "blank"comboboxes.  This is a function of Element Binding and has been resolved by the recommended solution of binding ItemSources through codebehind.  You may close this thread.