CodingSeb.ExpressionEvaluator Advanced Customization

The CodingSeb.ExpressionEvaluator allows you some deeper customizations of the parsing process.

• You can do customization, which is mostly available by inheritance.
• Most of the class is now in protected visibility in place of private and the majority of init and parsing methods are now virtual.

Let's consider we want to use and and or operator instead of && and || and to do so we need to add a new class and inherit it from the ExpressionEvaluator.

public class XExpressionEvaluator : ExpressionEvaluator
{
    protected override void Init()
    {
        operatorsDictionary.Add("and", ExpressionOperator.ConditionalAnd);
        operatorsDictionary.Add("or", ExpressionOperator.ConditionalOr);
        operatorsDictionary.Remove("&&");
        operatorsDictionary.Remove("||");
    }
}

As you can see that we have added and and or operators to the dictionary and then removed the && and ||.

The following example shows the usage of and and or operators.

public static void Example1()
{
	ExpressionEvaluator evaluator = new XExpressionEvaluator();

	List<string> expressions = new List<string>()
	{
		"true and true",
		"true and false",
		"false and true",
		"false and false",
		"true && true",
		"true or true",
		"true or false",
		"false or true",
		"false or false",
		"true || true"
	};

	foreach (var expr in expressions)
	{
		try
		{
			Console.WriteLine(expr);
			Console.WriteLine(evaluator.Evaluate(expr));
		}
		catch (Exception exception)
		{
			Console.WriteLine(exception);
		}
		finally
		{
			Console.WriteLine(string.Empty);
		}
	}
}