Q:

Keep focus on a row after DataGrid.ItemsSource changed

I'd like to keep the focus on the selected row after the ItemsSource has changed. I think I'm almost done, but none of some accepted answers does work for me :(
This is my code:
public void UpdateItemsSource()
{
    IdentifySelectedError(); //get "selectedRowIndex"
    DataGridRow dgr = (DataGridRow)DataGrid.ItemContainerGenerator.ContainerFromIndex(selectedRowIndex);
    using (var context = new Context())
    {
        DataGrid.ItemsSource = context.Error.Take(100).ToList();
    }
    //Everything does not work:
    //DataGrid.SelectedIndex = selectedRowIndex;
    //dgr.MoveFocus(new TraversalRequest(FocusNavigationDirection.Next));
    //dgr.Focus();
    //DataGrid.Rows(dgr).Selected = true;
    //DataGrid.ScrollIntoView(dgr);
    //FocusManager.SetIsFocusScope(dgr, true);

}

What am I doing wrong?
EDIT:
I noticed that when I changed the ItemsSource, the selectedRowInde has the value 0. This is why it cannot set the focus on the previously selected Row. Any ideas how to catch that?

A:

Save the row index into another int and set the selected item to it (or something like that):
public void UpdateItemsSource()
{
    IdentifySelectedError(); //get "selectedRowIndex"
    using (var context = new Context())
    {
        DataGrid.ItemsSource = context.Error.Take(100).ToList();
    }
    MainDataGrid.SelectedItem = MainDataGrid.Items[indexOfRow];
    MainDataGrid.ScrollIntoView(MainDataGrid.Items[indexOfRow]);
}

