How to declare an array of objects in C#

Question

I have a very beginning C# question. Suppose I have a class called GameObject, and I want to create an array of GameObject entities. I could think of writing code like:

GameObject[] houses = new GameObject[200];

The compiler complains (assuming because of invalid syntax). Since this is XNA development, I load my texture in the LoadContent() method as follows:

 houses[0].Model = Content.Load<Model>("Models\\Building_01 Windowed");

where houses[0] should be a GameObject and can be loaded like this, but the compiler throws this error:

"Use the "new" keyword to create an object instance"

"Check to determine if the object is null before calling the method"

There must be something wrong with my initialization.

Answer 1

The issue here is that you've initialized your array, but not its elements; they are all null. So if you try to reference houses[0], it will be null.

Here's a great little helper method you could write for yourself:

T[] InitializeArray<T>(int length) where T : new()
{
    T[] array = new T[length];
    for (int i = 0; i < length; ++i)
    {
        array[i] = new T();
    }

    return array;
}

Then you could initialize your houses array as:

GameObject[] houses = InitializeArray<GameObject>(200);

Answer 2

With LINQ, you can transform the array of uninitialized elements into a new collection of created objects with one line of code:

var houses = new GameObject[200].Select(h => new GameObject()).ToArray();

Actually, you can use any other source for this, even generated sequence of integers:

var houses = Enumerable.Repeat(0, 200).Select(h => new GameObject()).ToArray();

However, the first solution seems more readable to me, although the type of the original sequence is not important.

Answer 3

You are creating an array of null references. You should do something like:

for (int i = 0; i < houses.Count; i++)
{
    houses[i] = new GameObject();
}