实体框架向我的班级添加属性（头顶）

Question

I'm trying to create a datastructure with entity framework to basically store property values of my objects. I want users to add properties to a class at runtime. The properties can be of different datatypes. (string/int/float etc..)

So I thought I needed some tables/classes as defined in the image below. So my Object class contains a list of properties that are of a type defined in de propertydefinition class.

One hard thing is that values are stored in the table of the datatype of the propertie. (So a conditional foreignKey?)

Please give me some pointers on how to implement this by using Fluent API. Or other ideas on this subject. (I guess I won't be the first ;)

Werner

Answer 1

The EF entity model cannot be changed during Runtime (or at least is not designed for). You could use an infrastructure to store propertyname/propertyvalye with EF but I think is not the right choice (you lose most of the functionalities).

The best choice could be a NoSQL db, ADO.Net or, if only some objects can be personalized and other are fixed you could store the personalizable objects in XML/JSON in a text field.

Answer 2

I found this link

This helped me solve my "Table Per Type" question. I now have:

public abstract class PropertyBase
{
    public int PropertyID { get; set; }
    public string Name { get; set; }
}

public class TextProperty : PropertyBase
{
    public string Value { get; set; }
}

public class IntProperty : PropertyBase
{      
    public int Value { get; set; }
}

In My Database Context I added:

        modelBuilder.Entity<PropertyBase>()
            .HasKey(p => p.PropertyID)
            .ToTable("Properties");                    

        modelBuilder.Entity<IntProperty>()
            .ToTable("IntProperties");

        modelBuilder.Entity<TextProperty>()
            .ToTable("TextProperties");

The different types of properties (sub classes) are now stored in separate tables. The main abstract class contains all the other info. This worked fine for me.