public class Customer {
    public int Id { get; set; }
    public string Name { get; set; }
    public int AddressId { get; set; }  
    public int ContactId { get; set; }
    public Address Address { get; set; }
    public Contact Contact { get; set; }
}

public class Address {
    public int Id { get; set; }
    public string Address1 {get;set;}
    public string Address2 {get;set;}
    public string City {get;set;}
    public string State {get;set;}
    public int ZipCode {get;set;}
    public IEnumerable Customer {get;set;}
}

public class Contact {
    public int Id { get; set; }
    public string Name { get; set; }
    public IEnumerable Customer {get;set;}
}

using (var conn = GetOpenConnection())
{
    var query = _contextDapper
        .Query($@"
            SELECT c.Id, c.Name, 
                c.AddressId, a.Id, a.Address1, a.Address2, a.City, a.State, a.ZipCode,
                c.ContactId, ct.Id, ct.Name
            FROM Customer c
            INNER JOIN Address a ON a.Id = c.AddressId
            INNER JOIN Contact ct ON ct.Id = c.ContactId", 
            (c, a, ct) =>
            {
                c.LogType = a;
                c.Contact = ct;
                return c; 
            }, splitOn: "AddressId, ContactId")
        .AsQueryable();

    return query.ToList();          
}