Entity Framework Core - storing action delegate-CodePudding

I use Entity Framework Core. I have entity with action delegate property:

public class Student
{
    public int Id { get; set; }
    public string Name { get; set; }
    public Action<string, int, decimal, int> RateAction { get; set; }
}

var student1 = new Student();
student1.Id = 1;
student1.Name = "Test 1";
student1.RateAction = (s, a, b, c) =>
{
  var m = a * c   b;
  s = $"{s} - {m}";
};

var student2 = new Student();
student1.Id = 2;
student1.Name = "Test 2";
student1.RateAction = (s, a, b, c) =>
{
  b = c * b / a;
};

Student entity is part Entity Framework context:

public class MyContext : DbContext
{
    ...
    public DbSet<Student> Students { get; set; }
    ...
}

I have fluent API configuration for the entity:

public class StudentConfiguration : IEntityTypeConfiguration<Student>
{
    public void Configure(EntityTypeBuilder<Student> builder)
    {
        builder.ToTable("Student");
        builder.HasKey(x => x.Id);
        builder.Property(x => x.Name).IsRequired();

        // Add config for RateAction property
    }
}

How store RateAction property in database and configure with entity framework?

CodePudding user response：

I think you need a Table for the property RateAction and in the Table Student you need a FK for RateAction.

CodePudding user response：

I would recommend not storing the action. Databases are for data and code is for configuring functionality/actions. Instead, store instances of inherited Student classes, that implement the desired action/logic and return a calculated value, which can be further formatted as needed:

public abstract class Student
{
    public int Id { get; set; }
    public string Name { get; set; }
    public abstract decimal RateAction(int a, decimal b, int c);
}

public class MultiplyingStudent : Student
{
    public override decimal RateAction(int a, decimal b, int c) => a * c   b;
}

public class DividingStudent : Student
{
    public override decimal RateAction(int a, decimal b, int c) => c * b / a;
}

These child classes, and any others, will store just fine inside your DbSet of Student objects:

var m = new MultiplyingStudent();
var d = new DividingStudent();

...

var context = new MyContext();
context.Students.Add(m);
context.Students.Add(d);

EF will add a discriminator column as a way to help it turn rows back into instances once you do a select statement:

var x = context.Students.Select(s => s.Id == <int>);
var result = x.RateAction(<int>, <decimal>, <int>);