N-Tier sample

What I mostly do is the following:

- Create a library for the DataLayer
- Create a library for the BusinessLayer
- Create a project for the PresentationLayer

If you want to use the SqlCommand etc.. You put this in the datalayer. From the busineslayer you connect to the datalayer and ask for information (or save whatsoever).

The data you receive like a single datareader, I use this as parameter:
public T SomeMethod<T>(Func<IDataRecord, T> add) where T : class

And inside the call for loading, returning the data:
T record = default(T);
            using (SqlDataReader reader = cmd.ExecuteReader())
            {
                if (reader.Read())
                {
                    record = add(reader);
                }
            }

In this way you can use an delegate to tell the datalayer how you want to receive your data. For suggestion a Model. You create models in your domain (you can put it in the BusinessLayer). And you can fill them from the datalayer end.
Just when you call the SomeMethod(), you can do the following:

Person perso = DataLayer.SomeMethod(x => new Person(x));

Inside the model you create a constructor which accepts IDataRecord, from there you can get the data you need.

In this way you can fill your model and keep that separation of concern.

Now you can pass it on to the presentation layer.
I think from there it makes sense.