Question

What is wrong with this (in C# 3.0):

List<double> x = new List<double> { 0.0330, -0.6463, 0.1226, -0.3304, 0.4764, -0.4159, 0.4209, -0.4070, -0.2090, -0.2718, -0.2240, -0.1275, -0.0810, 0.0349, -0.5067, 0.0094, -0.4404, -0.1212 };
List<double> y = new List<double> { 0.4807, -3.7070, -4.5582, -11.2126, -0.7733, 3.7269, 2.7672, 8.3333, 4.7023,0,0,0,0,0,0,0,0,0 };

List<double[,]> z = new List<double[,]>{x,y}; // this line

The error produced is:

Error: Argument '1': cannot convert from 'System.Collections.Generic.List<double>' to 'double[*,*]' 

Help needed.

Answer 1

var z = new List<List<double>> { x, y };

However if you want to store your two lists in a twodimensional array ([,]) this is your anwser. You will have to convert it manually as shown there:

public static T[,] To2dArray(this List<List<T>> list)
{
    if (list.Count == 0 || list[0].Count == 0)
        throw new ArgumentException("The list must have non-zero dimensions.");

    var result = new T[list.Count, list[0].Count];
    for(int i = 0; i < list.Count; i++)
    {
        for(int j = 0; j < list.Count; j++)
        {
            if (list[i].Count != list[0].Count)
                throw new InvalidOperationException("The list cannot contain elements (lists) of different sizes.");
            result[i, j] = list[i][j];
        }
    }

    return result;
}