C#

public void SaveChanges()
{
    if (Company.Id == 0)
    {
        // Would you assign the ID of the logged in user here before calling the back end?? In EVERY Save method everywhere??
        Company.CreatedById = CurrentUser.Id;

        Company.Id = AppCore.BizObject.AddCompanyAsync(Company);
    }
    else
    {
        // Would you assign the ID of the logged in user here before calling the back end?? In EVERY Save method everywhere??
        Company.LastModifiedById = CurrentUser.Id;

        AppCore.BizObject.UpdateCompanyAsync(Company);
    }
}

// arrange
          ListXwithErrors node = new ListXwithErrors();

          // act
          node = null;
          // assert
          Assert.IsNull(node);

List<string> list = new List<string>();  // is an "empty" list.

bool isEmpty = (list.Count == 0);  // tests for an "empty" list

List<string> list = new List<string>();

public class Car
    {
        private string model;
        private string colour;

        public Car(string model, string colour)
        {
            this.model = model;
            this.colour = colour;
        }

[TestClass]
   public class CarTestClass
   {
       [TestMethod]
       public void TestCar()
       {
           // arrange
           Car mycar = new Car("Renault", "flame red");
           Car myothercar = new Car("Volvo");

           //act
           string mymodel = mycar.Model;
           string mycolour = mycar.Colour;
           string myothermodel = myothercar.Model;
           string myothercolour = myothercar.Colour;

           // assert
           Assert.AreEqual("Renault", mymodel);
           Assert.AreEqual("flame red", mycolour);
           Assert.AreEqual("Volvo", myothermodel);
           Assert.IsNull(myothercolour);
       }

[TestMethod]
public void Index()
{
    // Arrange
    List<string> list = new List<string>();

    // Act
    bool isEmpty = (list.Count == 0);

    // Assert
    Assert.AreEqual(0, list.Count());

}

public int Length()
{
    return size;
}

public void NumberOfObjects()
{
    // Arrange
    List<int> lenght = new List<int>();

    // Act
    lenght.Count();

    // Assert

}

IN mine.dll:
...
extern "C"
__declspec(dllexport)
int Square(int a) {
    return a*a;
}