Question

I need to create expressions at runtime which are depend on queries. Enums has implicit operator of <= however when I build expression of it I get exception which this operator don’t exist

public enum A
{
    A1,
    A2,
    A3
};

public class AA
{
    public A myA { get; set; }
    public int myB { get; set; }
};

ParameterExpression pe = Expression.Parameter(typeof(AA), "p");

 Expression.LessThanOrEqual(Expression.Property(
                                  pe,
                                  typeof(AA).GetProperty("myA")),
                                  Expression.Constant(A.A1, typeof(A)));

is it possible to create this expression?

Answer 1

It seems the <= operator isn’t defined on the enum, but on the enum type, which is integer. So in your case you could use

Expression.LessThanOrEqual(Expression.Convert(Expression.Property(
    pe,
    typeof(AA).GetProperty("myA")), typeof(int)),
    Expression.Convert(Expression.Constant(A.A1, typeof(A)), typeof(int)));