Dobra, tak konkretne- mam jiz openfiledialog a ten nacteny soubor potrebuji nejak dostat do pole abych s nim pak mohl dale pracovat:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;

namespace Graf_ze_souboru
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
            Stream soub;

        private void button1_Click(object sender, EventArgs e)
        {
            string cesta = "";
            DialogResult res = openFileDialog1.ShowDialog();
            if (res == DialogResult.OK)
                cesta = openFileDialog1.FileName;
            soub = new FileStream(cesta, FileMode.Open);
            StreamReader cti = new StreamReader(soub);
        }
    }
}