Storing unitialized object in array, then constructing?

Question

I dont think this is possible in c# but ill post it anyway.

Given my code

Control ctrlA = null, ctrlB = null;
var ctrlCollection = new []{ctrlA, ctrlB};
for (int i = 0; i < ctrlCollection.length;i++)
ctrlCollection[i] = new Control();

Is it possible to to construct these two objects and have them referenced to their respective variables (ctrlA and ctrlB)? As it stands, ctrlA and ctrlB will still have null references.

Are you trying to defer your object initialization? If you are on .NET 4.0+ have a look at Lazy Initialization — Paolo Moretti
– Paolo Moretti, Commented Jun 27, 2012 at 13:39

Tim S. · Accepted Answer · 2012-06-27 13:36:50Z

4

No, it's not. (at least, not unless you want to work with pointers or something) Will this work for you?

var ctrlCollection = new Control[2];
for (int i = 0; i < ctrlCollection.Length; i++)
    ctrlCollection[i] = new Control();
Control ctrlA = ctrlCollection[0], ctrlB = ctrlCollection[1];

answered Jun 27, 2012 at 13:36

Tim S.

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2 Comments

KennyZ Over a year ago

Beat me to it...I type too slow.

Sumo Over a year ago

+1 Correct and provides a solution, too. My answer doesn't even answer the question. I should downvote myself.

Gerrie Schenck · Accepted Answer · 2012-06-27 13:35:46Z

2

This won't work. The collection only stores references to its content, in your case ctrlA and ctrlB. When the statement ctrlCollection[i] = new Control(); is executed, this reference is replaced by another one.

ctrlA will still point to the original ctrlA reference (being null), ctrlCollection[i] points to a newly initialized Control object.

answered Jun 27, 2012 at 13:35

Gerrie Schenck

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Comments

Sumo · Accepted Answer · 2012-06-27 13:36:16Z

0

This is essentially the same as explicitly defining the length of the array. There's no need to add nulls to the array and then later overwrite null with a newly instantiated Control in the array item.

var ctrlCollection = new Control[2];
for (int i = 0; i < ctrlCollection.Length; i++)
    ctrlCollection[i] = new Control();

answered Jun 27, 2012 at 13:36

Sumo

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Comments

KennyZ · Accepted Answer · 2012-06-27 13:40:46Z

0

var ctrlCollection = new []{ctrlA, ctrlB}; 
for (int i = 0; i < ctrlCollection.length;i++) 
{
    ctrlCollection[i] = new Control();
} 
Control ctrlA = ctrlCollection[0];
Control ctrlB = ctrlCollection[1];

Can't imagine why you'd want to, but this should do what I think you are asking.

answered Jun 27, 2012 at 13:40

KennyZ

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Comments

Martin Liversage · Accepted Answer · 2012-06-27 13:52:24Z

0

Assuming that the size of you collection is fixed you can do this:

Control ctrlA, ctrlB;
var controls = new[] {
  ctrlA = new Control(),
  ctrlB = new Control()
};

This requires that the Control variables are declared in the same scope as the Control array is initialized.

edited Jun 27, 2012 at 13:52

answered Jun 27, 2012 at 13:43

Martin Liversage

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