Constructor not creating object

So i'm trying to create a building prototype and adding that to a list. However after i create the building and try to add it to the list I get a null reference error on line 7 of createAllBuildings
Might be important, so the createAllBuildings function is in my worldcontroller class and the constructor is in a non monobehavior building data class.
Debug.Log(b) = Building
But I cannot access any of b's variables.
Debug.Log in constructor = this.buildingName: Empty movecost: 1 width: 1 height: 1
NullReferenceException: Object reference not set to an instance of an object
WorldController.createAllBuildings () (at Assets/WorldController.cs:185)

thanks!

Code (CSharp):

1.  
2.     //Create all buildings
3.     public void createAllBuildings()
4.     {
5.         Building b = new Building("Empty", 1f, 1, 1);
6.         Debug.Log(b);
7.         Building.BuildingPrototypes.Add("Empty", b);
8.     }

Code (CSharp):

1.  
2.     public Building(string objectType, float movecost, int width, int height)
3.     {
4.         this.buildingName = objectType;
5.         this.moveCost = movecost;
6.         this.width = width;
7.         this.height = height;
8.         Debug.Log("this.buildingName: " + objectType + buildingName + " movecost: " + movecost + " width: " + width + " height: " + height);
9.     }

 

Its hard to understand whats going on, is the following a static function:

Code (CSharp):

1.       Building.BuildingPrototypes.Add("Empty", b);

Because if it isnt your calling a function that doesnt exist. a full code of building would be useful to see...