How to create expression tree returning restricted set of properties, based on convention?

Question

I need to create an expression tree returning Expression<Func<TDataStructure, Double[]>> expression. Tricky part about it, is that TDataStructure is generic what implies, that each passed class contains different set of properties. I need to get properties of type Double? and names starting with specific string, like "output".

Simple example case (concrete class):

Expression<Func<ConcreteDataStructure, Double[]>> expression =
    structure => new Double[] {
         structure.inputProperty1.Value,
         structure.outputProperty1.Value,
         structure.outputProperty2.Value
    };

where: structure.inputProperty1.Value, structure.outputProperty1.Value, structure.outputProperty2.Value are of type Double?

My case:

1. I do not know how many properties of type Double? are in TDataStructure

2. I need to get only these of type Double?, starting with "output"

3. Expression will be used in IQueryable<TDataStructure> Select method for projection of each sequence element into new form.

Answer 1

Try this:

public static Expression<Func<T, Double[]>> BuildExpression<T>()
{
    ParameterExpression param = Expression.Parameter(typeof(T));
    Expression[] array = typeof(T).GetProperties()
        .Where(p => p.Name.StartsWith("input") || p.Name.StartsWith("output"))
        .OrderBy(p => p.Name)
        .Select(p => (Expression)Expression.Property(Expression.Property(param, p), "Value"))
        .ToArray();

    Expression body = Expression.NewArrayInit(typeof(Double), array);

    return Expression.Lambda<Func<T, Double[]>>(body, param);
}