How to read a txt file into a two-dimensional array

You can use String.Split method with options set to RemoveEmptyEntries, which would split each line into separate items. Then fill jagged array with data obtained in that way.

Here is the code which does that - type lines and finish with a line consisting of single dash (-):
class Program
{

    static void Main(string[] args)
    {
        List list = new List();

        while (true)
        {
            string line = Console.ReadLine();
            if (line == "-")
                break;
            else list.Add(line);
        }

        string[] lines = list.ToArray();
        string[][] cells = new string[lines.Length][];

        for (int i = 0; i < cells.Length; i++)
            cells[i] = lines[i].Split(new char[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries);

        Console.WriteLine("------------------------------------");
        for (int i = 0; i < cells.Length; i++)
        {
            for (int j = 0; j < cells[i].Length; j++)
                Console.Write("[{0}] ", cells[i][j]);
            Console.WriteLine();
        }
        Console.WriteLine("------------------------------------");

    }
}

Input:

line1
line2
line3
 
col1 col2 col3 col4
1 3 12 63
83 10 19 14
21 34 87 54
-

Output:
------------------------------------
[line1]
[line2]
[line3]

[col1] [col2] [col3] [col4]
[1] [3] [12] [63]
[83] [10] [19] [14]
[21] [34] [87] [54]
------------------------------------

You can skip headers printing by starting the printout loop from specified index (e.g. 1 instead of 0).