private void dataGrid_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
    DependencyObject dep = (DependencyObject)e.OriginalSource;
           
    while ((dep != null) && !(dep is DataGridRow))
    {
        dep = VisualTreeHelper.GetParent(dep);
    }

    if (dep == null)
        return;

    if (dep is DataGridRow)
    {
        DataGridRow dataGridRow = dep as DataGridRow;               
        //tu was
    }            
}

<DataGrid.CellStyle>
    <Style>
        <EventSetter Event="DataGridCell.MouseDoubleClick"
            Handler="dataCell_MouseDoubleClick"/>
    </Style>
</DataGrid.CellStyle>

void dataCell_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
    DataGridCell cell = e.Source as DataGridCell;
}