Dynamic and Interop#

Advantages#

Interoperability with dynamic languages and frameworks

dynamic d = "Test";
Console.WriteLine(d); // Output: Test
d = d.ToUpper();
Console.WriteLine(d); // Output: TEST
d = 3; // d changes its runtime type to int
Console.WriteLine(d); // Output: 3
d += 7;
Console.WriteLine(d); // Output: 10

Disadvantages#

Deactivates type checking and IntelliSense, Everything compiles:

dynamic speaker = new NonSenseTalker();
speaker.HelloWorld();
speaker.Im().Just().Demonstrating().This().Feature();
speaker.GoodBye();

Run python in C#

static dynamic Calculate(string expression) {
  var engine = Python.CreateEngine();
  return engine.Execute(expression);
    /*To execute Script
    engine.Execute("import pythonDemo\n pythonDemo.factorial(1000)");
    */
}

static void Main(string[] args) {
  dynamic result = Calculate("2 * 3");
  Console.WriteLine("result : {0}", result);
}

ExpandoObject#

ExpandoObjects implements dynamic properties

dynamic o = new ExpandoObject();
o.Test = 123;
o.Foo = "hallo";
o.Bar = new object();
o.F = (Action)(() => Console.WriteLine("Action done"));
o.F()
Console.WriteLine(o.Foo);

Custom Dynamic Types#

public class World : DynamicObject
    {
        private Cities _cities;

        public World(Cities cities)
        {
            _cities = cities;
        }

        public override bool TryGetMember(GetMemberBinder binder, out object result)
        {
            result = _cities.CityList.FirstOrDefault(city => city.Name == binder.Name)
                     ?? (object) $"The city \"{binder.Name}\" does not exist!";

            return true;
        }

        public override bool TrySetMember(SetMemberBinder binder, object? args)
        {
            City city = null;
            try
            {
                city = _cities[binder.Name];
            }
            catch (Exception e)
            {
                throw new InvalidOperationException($"The city \"{binder.Name}\" does not exist!");
            }

            try
            {
                var inputs = (args as string).Split(':');
                switch (inputs[0])
                {
                    case "Population":
                        city.Population = Convert.ToInt32(inputs[1]);
                        break;
                    case "Latitude":
                        city.Location.Latitude = Convert.ToDouble(inputs[1]);
                        break;
                    case "Longitude":
                        city.Location.Longitude = Convert.ToDouble(inputs[1]);
                        break;
                    default: throw new ArgumentException("Invalid property assigned");
                }
            }
            catch (Exception e)
            {
                throw new ArgumentException("Invalid property value passed");
            }

            return true;
        }
    }

public virtual bool TryInvokeMember(InvokeBinder binder, Object[] args , out Object result) so you can call dynamic methods like duck.Quack();

P/Invoke#

Allows you to execute unmanaged/native code for example you can call a C++ DLL. 1. Locates the DLL containing the function. 2. Loads the DLL into memory. 3. Locates the address of the function in memory and pushes its arguments onto the stack, marshaling data as required. 4. Transfers control to the unmanaged function

class Test {
    [DllImport("user32.dll)"]
    static extern int MessageBox(uint hWnd, string text, string caption, uint type);
    static void Main() {
      MessageBox(0, "Calling native code isn't that cool?", "", 1,
    }
}

COM interoperability#

COM stands for "Component Object Model". Mostly used to control Microsoft products, windows word etc. So for example you can build plugins.

using Word = Microsoft.Office.Interop.Word
var word = new Word.Application();
word.Documents.Add();
word.ActiveDocument.SaveAs("test.doc");