C# 4.0 使用枚举生成lessthanRequal表达式

我需要在运行时创建依赖于查询的表达式。Enums具有隐式运算符，似乎

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)));

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