Hello Chris,

Thank you for the thread reference you have provided.

I have tested the selection behavior you have described, along with the information from the referenced thread and I can suggest you to use the SelectedItems property of the XamDataGrid for selecting all records by populating the SelectedItems.Records respectively.

This can be done within a Command for Control + A key binding, for example:

XAML:

<igDP:XamDataGrid.InputBindings>
    <KeyBinding Key="A" Modifiers="Control" CommandParameter="{Binding ElementName=dataGrid}">
        <KeyBinding.Command>
            <local:SelectAllCommand />
        </KeyBinding.Command>
    </KeyBinding>
</igDP:XamDataGrid.InputBindings>

Code-behind:

public class SelectAllCommand : ICommand
{
    public event EventHandler CanExecuteChanged;
    public bool CanExecute(object parameter)
    {
        return true;
    }
    public void Execute(object parameter)
    {
        var grid = (parameter as XamDataGrid);
        grid.SelectedItems.Records.AddRange(grid.Records.ToArray());
    }
}

Another approach would be to execute the same code in a button click

private void Button_Click(object sender, RoutedEventArgs e)
{
    dataGrid.SelectedItems.Records.AddRange(dataGrid.Records.ToArray());
}

I have attached a sample application that demonstrates the approach from above by using 20,000 records.

If you have any questions, please let me know.