Converting List<T> to Array (multidimensional) [duplicate]

Question

Possible Duplicate:
How can I convert a list<> to a multi-dimensional array?

I want to have an array in form of double[,] for this purpose since I do not know what will be the length of this array, I want to make a List first then later using List<T>.ToArray() convert it to double[,]:

public double[,] FilterClampedData(double[,] data)
{
    var finalData = new List<double[]>();

    //Do some stuff on parameter

    return finalData.ToArray(); ///Does not compile :(
}

Answer 1

Since ToArray returns a one-dimensional array, there is no wonder why this does not compile. If you were returning double[][], it would compile, however. You could also build your 2-D array manually with two nested loops:

var R = finalData.Count;
var C = finalData[0].Length;
var res = new double[R, C];
for (int r = 0 ; r != R ; r++)
    for (int c = 0 ; c != C ; c++)
        res[r, c] = finalData[r][c];
return res;

The code above assumes that you have at least one item in the finalData, and that the length of all lists inside finalData is the same.

Answer 2

1. Instantiate a new double array with the largest size [length of the list, largest array length in the list]
2. Walk through the list with double for cycle (first on the list, the nested on the current list item) and fill the new array