How to declare an array of objects in C#

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 ini开发者_如何学Gotialization.

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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);

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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.

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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();
}

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For people still looking

    Object[] obj = {
        new { key = "key", value = "value"},
        new { key = "key", value = "value"},
        new { key = "key", value = "value"},
        new { key = "key", value = "value"}
    };

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I guess GameObject is a reference type. Default for reference types is null => you have an array of nulls.

You need to initialize each member of the array separatedly.

houses[0] = new GameObject(..);

Only then can you access the object without compilation errors.

So you can explicitly initalize the array:

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

or you can change GameObject to value type.

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The reason this is happening is because initializing an array does not initialize each element in that array. You need to first set houses[0] = new GameObject() and then it will work.

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you need to initialize the object elements of the array.

GameObject[] houses = new GameObject[200];

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

Of course you initialize elements selectively using different constructors anywhere else before you reference them.

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Everything you have looks fine.

The only thing I can think of (without seeing the error message, which you should have provided), is that GameObject needs a default (no parameter) constructor.