C# add custom attributes for a parent's property in an inherited class

Question

I'm displaying Business Object in generic DataGrids, and I want to set the column header through a custom attribute, like:

class TestBo
 {
    [Header("NoDisp")]
    public int ID {get; set;}

    [Header("Object's name")]
    public String Name { get; set; }
}

So far, so good, but I'd also want to separate my display from my data, by inheritance:

class TestBO
{
   public int ID {get; set;}
   public String Name { get; set; }
}

class TestPresentationBO : TestBO
{
  //Question: how to simply set the Header attribute on the different properties?
}

I see a solution via reflection with a SetCustomAttribute in the Child constructor, but it will be cumbersome, so is there a simple and elegant trick for this problem?

Please prevent me from breaking the data/presentation separation ;o)

Answer 1

For C# 6.0 you can easily hide inherited members and introduce your own attributes. This might, however, hide any attributes on the original property. Also this simplified syntax makes the property read-only, so you might need to pipe the get/set yourself.

public class User
{
    public string Login { get; set; }
}


public class UserDetail : User
{
    [Display(Name = "Login:")]
    public new string Login => base.Login;
}

Answer 2

Make the properties in TestBo virtual and override them in TestPresentationBO. That way you can add the attributes.

Answer 3

Question: how to simply set the Header attribute on the different properties?

There is no way to set an attribute on an inherited member the way you have suggested, since attributes are specific to a type. SetCustomAttribute won't help you - it's only any good when you construct new types at runtime. Once an attribute has been compiled in you cannot change it at runtime, since it's part of the metadata.

If you want to maintain the separation you will have to find another way.

(You could make the properties virtual, override them in the Presentation class and add attributes on the overrides, but this looks dodgy and doesn't really separate anything - you end up with a complete TestBO class in your TestPresentationBO anyway...)

Answer 4

Just thinking, can't you solve this with partial classes and the MetadatatypeAttribute? MVC2 uses this pattern for Model validation.