Evaluate object tree expressions

Question

 

Hi!

 

I have this:

 

IList<int> numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

 

Expression parameter = Expression.Parameter(typeof(int), "x");

 

BinaryExpression binaryExpression = Expression.Or(

ConditionalExpression.LessThan(parameter, MemberExpression.Constant(5)),

ConditionalExpression.GreaterThan(parameter, MemberExpression.Constant(7)));

 

what should i do next to evalute the expression "binaryExpression" on the list "numbers"?

 

This binary expression would find in numbers where x < 5 | x > 7...

 

Best Regards!

 

Felipe

Answer 1

I think this is what you are trying to achieve:

Code Snippet

IEnumerable<int> numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

ParameterExpression parameter = Expression.Parameter(typeof(int), "x");
Expression<Func<int, bool>> expr = Expression.Lambda<Func<int, bool>>(
  Expression.Or(
    ConditionalExpression.LessThan(parameter, MemberExpression.Constant(5)),
    ConditionalExpression.GreaterThan(parameter, MemberExpression.Constant(7))),
  new ParameterExpression[] { parameter });

IEnumerable<int> results = numbers.Where(expr.Compile());
foreach (int i in results)
  Console.WriteLine(i);