Considering you are "new" to WPF, why are you bothering with "ExtendedGridControl" when WPF has a "native" datagrid control?
For all intents the "extended grid" is a "3rd party" grid that stood in until WPF got a "native" grid (a few years ago).
Use the native WPF data grid control.
The DataGrid control - The complete WPF tutorial[
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