Question

I have a class MyDummyClass to which I’d like to pass some properties in form of a Lambda expression for a later evaluation. So what I can do something like

public class MyDummyClass<T>
{
    public MyDummyClass(Expression<Func<T, object>> property)
    {
        ...
    }
    ...
}

..and then use that class like new MyDummyClass<Person>(x=>x.Name), right?

But then I’d like to pass not only a single property but a list of properties. So I’d write my class like

public class MyDummyClass<T>
{
    public MyDummyClass(IEnumerable<Expression<Func<T, object>>> properties)
    {
        ...
    }
    ...
}

and I’d like to use it like new MyDummyClass<Person>(new[] { x=>x.Name, x=>x.Surname }) but unfortunately that doesn’t work! Instead I have to write

new MyDummyClass<Person>
     (new Expression<Func<Person, object>>[] { x=>x.Name, x=>x.Surname});

But this is a bit awkward to write, isn’t it? Of course, using params would work, but this is just a sample out of a more complicated piece of code where using params is not an option.
Does anyone have a better option to come out of this??

Answer 1

You could try:

public class MyDummyClass<T>
{
    public MyDummyClass(Expression<Func<T, object>> expression)
    {
        NewArrayExpression array = expression.Body as NewArrayExpression;
        foreach( object obj in ( IEnumerable<object> )( array.Expressions ) )
        {
            Debug.Write( obj.ToString() );
        }
    }
}

And then you would call it like this:

MyDummyClass<Person> cls = new MyDummyClass<Person>( item => new[] { item.Name, item.Surname } );

The problem is this won’t give you the value of the property because no actual Person instance it specified Doing a ToString on “obj” will give you the name of the property. I don’t know if this is what you’re after, but it maybe a starting point.