reading csv file c#

There are many open source CSV readers, and it's also easy to code your own.

For a start take look at codeplex.com: http://kbcsv.codeplex.com/

Or Codeproject tutorials: http://www.codeproject.com/KB/database/CsvReader.aspx

For sake of completion, here is my own utility class to read a line from a CSV file:

    /// <summary>
    /// Defines CSV reader states
    /// </summary>
    enum State
    {
        Initial, 
        Quote,
        Data,
        NestedQuote
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="CsvReader"/> class.
    /// </summary>
    /// <param name="inputStream">The input stream.</param>
    public CsvReader(Stream inputStream)
    {
        if (inputStream == null) 
            throw new ArgumentNullException("inputStream");

        reader = new StreamReader(inputStream);
    }

    /// <summary>
    /// Reads a single line of CSV data.
    /// </summary>
    /// <returns>Array of CSV fields</returns>
    public string[] Read()
    {
        var line = reader.ReadLine();
        var retval = new List<string>();

        if (line == null) 
            return null;

        var state = State.Initial;
        var text = new StringBuilder();

        foreach (var ch in line)
            switch (state)
            {
                case State.Initial:
                    if (ch == '"') 
                        state = State.Quote;
                    else if (ch == ',') 
                        retval.Add(string.Empty);
                    else
                    {
                        text.Append(ch);
                        state = State.Data;
                    }

                    break;

                case State.Data:
                    if (ch == ',')
                    {
                        retval.Add(text.ToString());
                        text.Length = 0;
                        state = State.Initial;
                    }
                    else 
                        text.Append(ch);

                    break;

                case State.Quote:
                    if (ch == '"')
                        state = State.NestedQuote;
                    else 
                        text.Append(ch);

                    break;

                case State.NestedQuote:
                    if (ch == '"')
                    {
                        text.Append('"');
                        state = State.Quote;
                        break;
                    }

                    state = State.Data;
                    goto case State.Data;
            }

        retval.Add(text.ToString());

        return retval.ToArray();
    }

    /// <summary>
    /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
    /// </summary>
    public void Dispose()
    {
        reader.Dispose();
    }

To make the matrix (untested):

var data = new List<string[]>();
string[] line;

using(reader = new CsvReader(stream))
  while((line = reader.Read()) != null)
    data.Add(line);

result = data.Select(row => row.Select(cell => int.Parse(cell)).ToArray()).ToArray();