CodingSeb.ExpressionEvaluator Additional Variables Declaration

The CodingSeb.ExpressionEvaluator library allows you to assign an expression to your custom variable by using the SubExpression.

The following example shows the usage of the SubExpression.

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

	evaluator.Variables["a"] = 4;
	evaluator.Variables["b"] = 7;
	evaluator.Variables["c"] = new SubExpression("a+b");
	evaluator.Variables["d"] = new SubExpression("c+3");

	List<string> expressions = new List<string>()
	{
		"a",
		"b",
		"c",
		"d",
		"d",
		"a + b",
		"c + 10"
	};

	foreach (var expr in expressions)
	{
		var result = evaluator.Evaluate(expr);
		Console.WriteLine($"{expr}:\t {result}\n");
	}
}

Let's execute the above code and you will see the following output.

a:       4

b:       7

c:       11

d:       14

d:       14

a + b:   11

c + 10:  21

In addition to Variables dictionary, the CodingSeb.ExpressionEvaluator also provides a Context property of type object that allows you to access all public properties, fields, and methods directly of that particular object assigned to the Context.

public static void Example2()
{
	ExpressionEvaluator evaluator = new ExpressionEvaluator();

	evaluator.Context = new Customer()
	{
		FirstName = "Mark",
		LastName = "Upston",
		BirthDate = new DateTime(1977, 12, 10)
	};

	List<string> expressions = new List<string>()
	{
		"FirstName + \" \" + LastName",
		"GetAge()",
	};

	foreach (var expr in expressions)
	{
		var result = evaluator.Evaluate(expr);
		Console.WriteLine($"{expr}:\t {result}\n");
	}
}

public class Customer
{
	public string FirstName { get; set; }
	public string LastName { get; set; }
	public DateTime BirthDate { get; set; }

	public int GetAge()
	{
		DateTime date = DateTime.Now;
		var age = date.Year - BirthDate.Year;
		if (BirthDate.Date > date.AddYears(-age)) age--;
		return age;
	}
}

Let's execute the above code, and you will see the following output.

FirstName + " " + LastName:      Mark Upston

GetAge():        43