public void CustomFunction() { var engine = new RecalcEngine(); engine.AddFunction(new TestCustomFunction()); // Shows up in enuemeration var func = engine.GetAllFunctionNames().First(name => name == "TestCustom"); Assert.NotNull(func); // Can be invoked. var result = engine.Eval("TestCustom(2,3)"); Assert.Equal(6.0, result.ToObject()); }