Code refactoring - NULL check

Part 1
Part 2
Part 3

Let’s look over the following code:

public class Foo
{
  SomeFoo _some;
  
  ...

  public int GetA()
  {
    if(_some == null)
    {
      return 0;
    }

    return _some.A;
  }

  public string GetB()
  {
    if(_some == null)
    {
      return null;
    }

    return _some.B;
  }

  public int GetTotalX()
  {
    if(_some == null)
    {
      return -1;
    }

    return _some.A + _some.C;
  }

}

We can see that the IF checks appears in more than one place. Even if is only a simple check, there can be a lot of places where it appears.
If we manage to extract this check in a generic method, than the code would be more legible. Because we don’t return each time the default value of an object we need to be able to return custom “default” value for the case when or object is null.
We can image a method that accept as parameter the object that we check if is null or not and another two parameters that represent the default value that need to be return and a generic function that return the expected value.

private TReturn ExecuteFuncOverObj<TReturn>(object obj, TReturn defaultValue, Func<TReturn> func)
{
  if( obj == null)
  {
    return defaultValue;
  }

  return func.Invoke();
}

In this way our code would look like this:

public class Foo
{
  SomeFoo _some;
  
  ...

  public int GetA()
  {
    return ExecuteFuncOverObj(_some, () => _some.A, 0);
  }

  public string GetB()
  {
    return ExecuteFuncOverObj(_some, () => _some.B, null);
  }

  public int GetTotalX()
  {

    return ExecuteFuncOverObj(_some, () => _some.A + _some.C, -1);
  }

}

If we need this behavior in other methods we could define a helper function or an extension method of Object.
Enjoy!
Part 1
Part 2
Part 3