Question

Ran into this issue on several occasions.

When finding SelectedItem or selected column on say right click menu or selecting combo box in a cell. The SelectedItem will be null or the previously selected row.

private void ComboBox_GotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e) {
// Correct  
m_BeginEditString = ((ComboBox)sender).SelectedValue.ToString(); 

// Wrong. selected item is last selected row, example clicking directly on combobox will not select row, and be null.
m_BeginEditRow = (RowItem)MyDataGrid.SelectedItem; 
}   

<DataGridTemplateColumn>
   <DataGridTemplateColumn.CellTemplate>
    <DataTemplate>
        <ComboBox SelectedItem="{Binding myItem, Mode=TwoWay, 
NotifyOnSourceUpdated=True, UpdateSourceTrigger=PropertyChanged}" 
ItemsSource="{Binding Source={StaticResource enum}}" 
SelectionChanged="ComboBox_Changed" 
LostKeyboardFocus="ComboBox_LostKeyboardFocus" 
GotKeyboardFocus="ComboBox_GotKeyboardFocus" />
        </DataTemplate>
   </DataGridTemplateColumn.CellTemplate>
 </DataGridTemplateColumn>

Answer 1

Solved by doing it a completely different way, thanks @Ramesh Muthiah for direction:

private void ComboBox_Changed(object sender, SelectionChangedEventArgs e) {
if (((ComboBox)sender).IsLoaded) { // disregard SelectionChangedEvent fired on population from binding
    if (e.RemovedItems.Count != 0) {
        for (Visual visual = (Visual)sender; visual != null; visual = (Visual)VisualTreeHelper.GetParent(visual)) { // Traverse tree to find corred selected item
            if (visual is DataGridRow) {
                DataGridRow row = (DataGridRow)visual;
                m_BeginEditRow = new MyRowItem((MyRowItem)row.Item); // Copy constructor, otherwise passed by reference
                break;
            }
        }
        MyEnum newItem = (MyEnum)e.AddedItems[0];
        MyEnum oldItem = (MyEnum)e.RemovedItems[0];
        if (m_BeginEditRow.Combo1 == newItem) {
            m_BeginEditRow.Combo1 = oldItem;
        } else {
            m_BeginEditRow.Combo2 = oldItem;
        }
        DoStuff(m_BeginEditRow, false);
    }
}

}