What is the best way to get a property and value with a particular attribute?

Question

Given this definition:

[UniqueId("Ident")]
public class MyClass : MyBase
{
    public int Ident{ get; }
}

What is the best way from the "MyBase" class to get the "UniqueId" attribute, find the matching property name and get the underlying value?

Answer 1

Wouldn't an abstract method / property in the base-class be more suitable?

public abstract int UniqueId {get;}

Via attributes, like so:

object GetUniqueId() // or int
{
    Type type = GetType();
    UniqueIdAttribute attrib = null;
    foreach(UniqueIdAttribute tmp in 
        type.GetCustomAttributes(typeof(UniqueIdAttribute), true))
    {
        attrib = tmp;
        break;
    }
    if (attrib == null) throw new InvalidOperationException();
    return type.GetProperty(attrib.PropertyName).GetValue(this, null);
    // perhaps cast here...         
}

Answer 2

I don't exactly understand why you'd want that attribute on the class. Wouldn't it be more obvious to add it to the property, like this:

public class MyClass
{
    [UniqueId]
    public int Ident{ get; }
}

You could access this value using something like

var identity = objectThatHasAnIdentity.GetId();

GetId could now be an extension method on object that implements a code similar to what Marc posted above