How to read dynamic properties from database

问题:

I will try to explain my scenario the best way I can. I have the following tables in my database:

Products{ProductId, CategoryId ...}
Categories{CategoryId ...}
CategoryProperties{CategoryPropertyId, CategoryId, Name ...}
PropertyValues{ProductId, CategoryPropertyId, Value ...}

So the goal is to have list of products which belongs to some category and each category can have 'n' number of properties with values in the 'PropertyValues' table. I have a query that returns data based on 'categoryId' so I can always get different results from the database:

For the CPU category:

intel i7 | CPU | Model | Socket | L1 Cash | L2 Cahs | etc.

For the HDD category:

samsung F3 | HDD | Model | Speed | GB | etc.

So based on categories from my query as a result I always can get different column numbers and names. For database access I use simple ADO.NET call to stored procedure that return result. But because query result is dynamic in it's nature I don't know what is a good way to read this data.

I made a Product entity but I am confused how to make it really :( I thought that I can make a Product entity and make other entities which inherit Product like Cpu, Hdd, Camera, PcCase, GraphicCard, MobilePhone, Gps etc.

but I think that it's stupid because I can end this with 200+ entities in domain.

What would you do in this situation?
How to read and where to put this dynamic properties?

UPDATE - some solution

All right based on @millimoose suggestion for Dictionary and @Tim Schmelter idea to use DataTable object I came to some solution.
Now... this works I get data read them and I can display them.
But I still need advice from smarter people than me on am I did this good or should I handle this better or I am made some spageti code. So here what I did:

public class Product
    {
        public Product()
        {
            this.DynamicProperties = new List<Dictionary<string, string>>();
        }

        public List<Dictionary<string, string>> DynamicProperties { get; set; }

    }
...
List<Product> products = new List<Product>();
...
using (SqlDataAdapter a = new SqlDataAdapter(cmd))
                {
                    DataTable t = new DataTable();
                    a.Fill(t);

                    Product p = null;

                    foreach (DataRow row in t.Rows)
                    {
                        p = new Product();
                        foreach (DataColumn col in t.Columns)
                        {
                            string property = col.ColumnName.ToString();
                            string propertyValue = row[col.ColumnName].ToString();

                            Dictionary<string, string> dictionary = new Dictionary<string, string>();

                            dictionary.Add(property, propertyValue);

                            p.DynamicProperties.Add(dictionary);
                        }

                        products.Add(p);
                    }
                }

回答1:

You have a product, a bunch of categories, and each category has a bunch of properties.

class Product
{
    public int Id { get; set; }
    public Category Category { get; set; }
    public List<ProductProperty> Properties { get; set; }
}

class Category
{
  public int Id { get; set; }
  public string Name { get; set; }
}

class ProductProperty
{
   public  int Id { get; set; }
   public  string Name { get; set; }
   public string Value { get; set; }
}

you could store the product properties in a list / dictionary

then you just add properties to the product

Properties.Add(new ProductionProperty() { Name="intel i7"});

or if its name/value

Properties.Add(new ProductionProperty() { Name="Speed", Value="150MB/s"});

回答2:

Your original approach

public class Product
{
    public List<Dictionary<string, string>> DynamicProperties { get; set; }
}

is quite good. I would use a custom collection though, with better naming so the intent is clearer.

---

You could also utilize C# 4.0's dynamic feature which more cool, but I'm not sure what benefit it gives in your case. You could do something like,

public class Product
{
    public List<dynamic> DynamicProperties { get; set; }
}

...

conn.Open();
using (var reader = cmd.ExecuteReader())
{
    var p = new Products();
    p.DynamicProperties = reader.AsDyamic().ToList();

    //or

    foreach (var item in reader.AsDynamic())
        yield return item;
}

// carry this extension method around
public static IEnumerable<dynamic> AsDynamic(this IDataReader reader)
{
    var names = Enumerable.Range(0, reader.FieldCount).Select(reader.GetName).ToList();
    foreach (IDataRecord record in reader as IEnumerable)
    {
        var expando = new ExpandoObject() as IDictionary<string, object>;
        foreach (var name in names)
            expando[name] = record[name];

        yield return expando;
    }
}

Somewhat related question: How to convert a data reader to dynamic query results