Question

I wanted to know how to apply a constructor on each element of an array that would then return an array of constructed objects. Specifically, I am working with C#’s TreeNode.
The concept I want is as follows:

string[] animals = {"dog","cat","mouse"};
TreeNode[] animalNodes = TreeNode[](animals);

Where TreeNode[](animals) would have the cumulative effect of

animalNodes[0] = TreeNode("dog");
animalNodes[1] = TreeNode("cat");
animalNodes[2] = TreeNode("mouse");

I know I can us foreach and load such a structure manually but if possible, I’m looking for the elegant ‘one line’ way. I have looked long and hard for how to do this but could not find anything.

Answer 1

Some LINQ will do the trick:

TreeNode[] animalNodes = animals.Select(a => new TreeNode(a)).ToArray();

The Select extension method executes the specified delegate (specified via a lambda here) on each member of the list, and creates a list of the results (IEnumerable<TreeNode> in this case). The ToArray extension method is then used to create an array from the result.

Alternatively, you can use LINQ’s query syntax:

TreeNode[] animalNodes = (from a in animals select new TreeNode(a)).ToArray();

The code generated by the compiler is the same for both these examples.