Reflection of an Object that is owned by another

Question

In my code I use a class called GenericField<T> which is used in all attributes of another class called Aplicacao. Until everything well, however, in another part of the code I need to get via Reflection the name of a class-specific attribute Aplicacao, which is actually an instance of GenericField<int>.

I tried the code below but did not get the expected answer (the attribute name that would be "id", instead I got "Gerericfield1"), the implementation of the two classes is soon after.

Aplicacao obj = new Aplicacao();
MessageBox.Show(obj.id.GetType().Name.ToString());

Class GenericField

[Serializable]
public class GenericField<T>
{
    private bool changeOldValue = true;

    private T _Value;
    public T Value
    {
        get { return _Value; }
        set
        {
            if (changeOldValue)
                _OldValue = value;

            _Value = value;
            changeOldValue = false;
        }
    }

    private T _OldValue;
    public T OldValue
    {
        get { return _OldValue; }
    }

    public override string ToString()
    {
        if (_Value == null)
            return "";
        return _Value.ToString();
    }
}

Class Aplicacao

public class Aplicacao : Objeto_DTL
{
    public Aplicacao()
    {
        _id = new GenericField<int>();
        _nome = new GenericField<string>();
        _descricao = new GenericField<string>();
        _criacao = new GenericField<DateTime>();
    }

    public override string ToString() { return _id.ToString() + " - " + _nome.ToString(); }

    private GenericField<int> _id;
    [DisplayName("ID")]
    public GenericField<int> id
    {
        get { return _id; }
        set { _id = value; }
    }

    private GenericField<string> _nome;
    [DisplayName("Nome")]
    public GenericField<string> nome
    {
        get { return _nome; }
        set { _nome = value; }
    }

    private GenericField<string> _descricao;
    [DisplayName("Descrição")]
    public GenericField<string> descricao
    {
        get { return _descricao; }
        set { _descricao = value; }
    }

    private GenericField<DateTime> _criacao;
    [DisplayName("Criação")]
    public GenericField<DateTime> criacao
    {
        get { return _criacao; }
        set { _criacao = value; }
    }
}

Answer 1

Now I understand what you need. I think, the way you implement the classes, it’s not possible.

Check it out: the property (which you want to recover the name) is of the type GenericField. When a method receives this value, all it knows is about the variable (of type GenericField). No way to know where it is referenced (as class property Aplicacao, and maybe another place).

In your case this is reflected in your call obj.id. [etc.]. You use the name of the property. Of course, I imagine, your final code won’t be like this (the property will be passed on, and it won’t be called by itself obj.{propriedade}).

An example of what you are wanting: you have a class A with a member named id and a call quantidade, both int. You pass both to one method (say calcular(int a, int b), and wants to discover, within the method, the names of these members within the class A. Is not possible.

The solution here would be to include within GenericField a field string propertyName, and maybe a field object Parent.

Answer 2

If you are using C# 6, use the reserved word nameof

As an example I suggest you follow the link below http://www.c-sharpcorner.com/UploadFile/7ca517/the-new-feature-of-C-Sharp-6-0-nameof-operator/

The operator nameof came together with C# 6 to facilitate the literal display of a property name.

Example: nameof(object. Ownership)

Answer 3

Hello, What you can also do is take the "Displayname" attribute from the property.

Ex :

Extension method:

public static T GetAttributeFrom<T>(this object instance, string propertyName) where T : Attribute
{
    var attrType = typeof(T);
    var property = instance.GetType().GetProperty(propertyName);
    return (T)property .GetCustomAttributes(attrType, false).First();
}

Code:

Aplicacao app = new Aplicacao();
var name = app.GetAttributeFrom<DisplayAttribute>("descricao").Name;

https://stackoverflow.com/questions/7027613/how-to-retrieve-data-annotations-from-code-programmatically

Answer 4

Please change the code to:

obj.Gettype(). Getproperty("id"). Name

--Edit

static void Main(string[] args)
    {
        Aplicacao obj = new Aplicacao();


        Console.WriteLine(GetName(() => obj.id));
    }

    public static string GetName<T>(Expression<Func<T>> e)
    {
        var member = (MemberExpression)e.Body;
        return member.Member.Name;
    }