private static void Add(Dictionary <string, List <ColumnInfo> > map, ColumnRole role, ColumnInfo info)
{
Contracts.AssertValue(map);
Contracts.AssertNonEmpty(role.Value);
Contracts.AssertValue(info);
if (!map.TryGetValue(role.Value, out var list))
{
list = new List <ColumnInfo>();
map.Add(role.Value, list);
}
list.Add(info);
}