支持用户定义的数据库字段的动态类

Question

I'm currently developing a WCF service in C# to serve as a basic API for an existing internal app. The API I'm developing specifically focuses on adding and deleting records from the database.

However, the application allows the end-user to alter the existing database structure by adding custom fields in each table.

This means that one departments' CUSTOMER table may look like this:

Id | FirstName | LastName | City | State | FavColor

While another departments' CUSTOMER table looks like this:

Id | FirstName | LastName | City | State | FavFood | FavMovie

How would I design a class to support the user-defined (Fav) fields given the structure above?

I considered using a Dictionary to handle the user-defined fields:

public class Customer
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string City { get; set; }
    public string State { get; set; }
    public Dictionary<string, string> UserDefinedFields { get; set; }
}

Is there a better (ie more established/best practice) for handling this requirement?

Answer 1

If the user defined fields were bounded you may well be served with inheritance using a type descriminator as a field. I'll dig out a Martin Fowler article for this. However, for extensibility using a vertical table (known as Entity Attribute Value) I have done something similar in the past. It worked just fine.

EDIT: It just occured to me that you could also serialize the instance and add it as a blob/text to a persistence medium. That way you can be fairly lax about schema. I think a document DB like Mongo would be good for this type of thing or a BLOB field in MSSQL