The primitive data types are predefined by the language, and they are named by reserved keywords. They represent the basic types of the language.
The ExpressionEvaluator manages the following list of C# primary types.
The ExpressionEvaluator allows you to call static methods on these types from within your expression as shown below.
public static void Example1()
{
var expression = new CompiledExpression("float.Parse('13.98')");
var result = expression.Eval();
Console.WriteLine("{0} ({1})", result, result.GetType());
}
You can add additional types by using the TypeRegistry class, which contains the methods for registering types and symbols. After adding a type of symbol you will also need to set the TypeRegistry property of the CompiledExpression instance before the expression is parsed.
The following example registers the symbol Guid as the type Guid.
public static void Example2()
{
var registry = new TypeRegistry();
registry.RegisterType("Guid", typeof(Guid));
var expression = new CompiledExpression("Guid.NewGuid()") { TypeRegistry = registry };
var result = expression.Eval();
Console.WriteLine("{0} ({1})", result, result.GetType());
}
You can also use your own data type using the same technique. Let's consider you have a simple class Point3D and you want to use the Point3D type in your expression.
public static void Example4()
{
var point = new Point3D() { X = 0.00, Y = 1.00, Z = 0.00 };
string expressionStr = "point3D.Y + 10";
var register = new TypeRegistry();
register.RegisterSymbol("point3D", point);
var expression = new CompiledExpression(expressionStr) { TypeRegistry = register };
Console.WriteLine("Result: {0}", expression.Eval());
}
class Point3D
{
public double X { get; set; }
public double Y { get; set; }
public double Z { get; set; }
}
Now when you run the above code you will see the following output.
Result: 11