C# List to Array Problem

Question

Still new to C# so be gentle :)

I have some code which reads in a CSV file and stores the output in a List. I used a List instead of an Array as the number of entries in the CSV is undetermined. Once the List is created from the file I then want to pass it to a Shell sort method as this is the purpose of the program. To do this I first want to convert the list to an array of integers. I have tried the .ToArray method but it doesnt seem to be working for me. I get an exception

Cannot Implicilty convert type String[][] to string[].

I know I am doing something stupid but cant seem to find out what... Any help would be appreciated.

//Import DAT file and format it.
public int[] ImportDat(string path)
{
    List<string[]> loadedData = new List<string[]>();

    loadedData.Clear();

    try
    {
        using (StreamReader readCSV = new StreamReader(path))
        {
            string line;
            string[] row; 

            while ((line = readCSV.ReadLine()) != null)
            {
                row = line.Split(',');
                loadedData.Add(row);
            }
        }
    }
    catch
    {
        MessageBox.Show("Import Failed. Please check the file is in the same folder as the executable");
    }

    string[] MyArray = loadedData.ToArray();

    //temp Array to return a value
    int[] numbers = new int[5] { 1, 2, 3, 4, 5 };

    return numbers;
}

Answer 1

It seems like you really want a one dimensional list of numbers from your CSV file, but you are treating each row separately right now. If that is the case then use:

 loadedData.AddRange(row);

instead of:

 loadedData.Add(row);

and declare loadedData as List<string>. Now you still would have to do the conversion to int, since your method returns a list of int.Using LINQ you could do:

List<int> results = loadedData.Select(s=> Convert.ToInt32(s)).ToList();

Your method also could be fully expressed with LINQ like this:

public int[] ImportDat(string path)
{
    List<int> result = File.ReadAllLines(path)
                           .Select(line => line.Split(','))
                           .SelectMany(s => s)
                           .Select( s=> Convert.ToInt32(s))
                           .ToList();
    return result;
}

Answer 2

Your variable loadedData is a List of string arrays. Calling .ToArray() on it will return a string[][] (2 dimensional array), not a string[].

Answer 3

Why don't you just use the list and convert the numbers right away?

public int[] ImportDat(string path)
{
     List<int> loadedData = new List<int>();

     loadedData.Clear();

     try
     {
        using (StreamReader readCSV = new StreamReader(path))
        {
            string line;
            string[] row;

            while ((line = readCSV.ReadLine()) != null)
            {
                row = line.Split(',');
                foreach(var token in row)
                {
                    loadedData.Add(Convert.ToInt32(token));
                }
            }
        }
     }
     catch
     {
        MessageBox.Show("Import Failed. Please check the file is in the same folder as the executable");
     }

     return loadedData.ToArray();
}

Answer 4

You are declaring loadedData as a list of string arrays. You should just do

List<string> loadedData = new List<string>();

Answer 5

The problem is that each item in your List, is an array of strings. it's not a list of string. hench, you should make your "MyArray" a two dimensional array of strings. in other words, an array of arrays of strings. so in short: string[][] MyArray = loadedData.ToArray();

Answer 6

Perhaps you can modify this code to suit your needs?

   List<int> numbersList = new List<int>();
        string input = "2,4,6,3";
        string[] numbersStringArray  = input.Split(',');
        foreach (var numberString in numbersStringArray)
        {
            numbersList.Add(Convert.ToInt32(numberString));
        }

        int[] numbersArray = numbersList.ToArray<int>();