Question

I have a data access class that loads reference data. Each type of entity will execute it’s own stored procedure and return a result set specific for that entity type. Then I have a method that maps the returned values from the datatable to the entity. All Entity Types have the same public properties of Code and Name how can I make this method generic to handle a type of entity? Something like this is what would presume but the properties are causing an error.

    private static T MapDataReaderToEntity<T>(IDataReader reader)
    {
        var entity = typeof (T);
        entity.Code = SqlPersistence.GetString(reader, "Code");
        entity.Name = SqlPersistence.GetString(reader, "Name");
        return entity;
    }

and I would call it with something like this.

_sourceSystem = MapDataReaderToEntity<SourceSystem>(_reader);

Answer 1

If your entities implement an interface with the Code and Name properties defined, you could potentially use something like:

private static T MapDataReaderToEntity<T>(IDataReader reader)
    where T : IEntity, new()
{
    T entity = new T(); // typeof(T) would return the System.Type, not an instance!
    entity.Code = SqlPersistence.GetString(reader, "Code");
    entity.Name = SqlPersistence.GetString(reader, "Name");
    return entity;
}

Without the interface, there is no way for the compiler to know about the Code or Name properties. You would need to revert to using Reflection or dynamic code, or some other less-than-ideal mechanism for determining these properties at runtime instead of at compile time.