Custom Attribute on property in C#

Question

I have a class Person with two properties

public sealed class Person
{
[Description("This is the first name")]
public string FirstName { get; set; }
[Description("This is the last name")]
public string LastName { get; set; }
}

In my console application code I'd like to get for each property of each instance the value of the Description Attribute.....

something similar to

Person myPerson = new Person();
myPerson.LastName.GetDescription() // method to retrieve the value of the attribute

Is it possible to do this task? Can someone suggest me a way? Best regards Fab

Answer 1

With exactly that syntax it isn't possible. It is possible by using Expression Trees... For example:

public static class DescripionExtractor 
{
    public static string GetDescription<TValue>(Expression<Func<TValue>> exp) 
    {
        var body = exp.Body as MemberExpression;

        if (body == null) 
        {
            throw new ArgumentException("exp");
        }

        var attrs = (DescriptionAttribute[])body.Member.GetCustomAttributes(typeof(DescriptionAttribute), true);

        if (attrs.Length == 0) 
        {
            return null;
        }

        return attrs[0].Description;
    }
}

and then:

Person person = null;
string desc = DescripionExtractor.GetDescription(() => person.FirstName);

Note that the value of person is irrelevant. It can be null and everything will work correctly, because person isn't really accessed. Only its type is important.