1

http://msdn.microsoft.com/ru-ru/library/ybsdta26(v=vs.110).aspx

http://www.dotnetperls.com/openfiledialog

http://www.dotnetperls.com/split

http://code.msdn.microsoft.com/101-LINQ-Samples-3fb9811b

private void button1_Click(object sender, EventArgs e)
 {
     int size = -1;
     DialogResult result = openFileDialog1.ShowDialog(); // Show the dialog.
     if (result == DialogResult.OK) // Test result.
     {
  string file = openFileDialog1.FileName;
  try
  {
      string text = File.ReadAllText(file);
      size = text.Length;
  }
  catch (IOException)
  {
  }
     }
     Console.WriteLine(size); // <-- Shows file size in debugging mode.
     Console.WriteLine(result); // <-- For debugging use.
 }

http://stackoverflow.com/questions/7387085/how-to-read-an-entire-file-to-a-string-using-c-sharp

string readContents;
using (StreamReader streamReader = new StreamReader(path, Encoding.UTF8))
{
     readContents = streamReader.ReadToEnd();
}

    public partial class Form1 : Form
    {
        //private PortfolioViewForm _pvForm ;
        private PortfolioManagerForm2 _pmForm;
        private readonly PortfolioManager _pm;

        public Form1()
        {
            InitializeComponent();
            _pm = PortfolioManager.Instance;
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            _pmForm = new PortfolioManagerForm2(_pm);
            _pmForm.Show();
        }

        private void btnSelectFile_Click(object sender, EventArgs e)
        {
            int size = -1;
            DialogResult result = openFileDialog1.ShowDialog(); // Show the dialog.
            if (result == DialogResult.OK) // Test result.
            {
                string file = openFileDialog1.FileName;
                try
                {
                    string text = File.ReadAllText(file);
                    size = text.Length;
                    txtFileSelected.Text = file;
                    //var sr = new StringReader(text);
                    //var lst = new List<string>();
                    //string str = string.Empty;
                    //while ((str = sr.ReadLine()) != null)
                    //{
                    //    lst.Add(str);
                    //}
                    //listFileLines.DataSource = lst;

                    string readContents;
                    var lst = new List<string>();
                    using (var streamReader = new StreamReader(file, Encoding.UTF8))
                    {
                        //readContents = streamReader.ReadToEnd();
                        while (!streamReader.EndOfStream)
                        {
                            //lst.Add(streamReader.ReadLine());
                            var s = streamReader.ReadLine();
                            if (s != null) listFileLines.Items.Add(s);
                        }
                    }
                    //listFileLines.DataSource = lst;

                }
                catch (IOException)
                {
                }
            }

        }
        
    }