read from arabic file

Question

hi all 
when I try to read file which written in arabic format ,I get only last line ...what's the problem.
The code:

            // Read the file and display it line by line in text box

            System.IO.StreamReader file =

               new System.IO.StreamReader("arabic.txt", Encoding.UTF8);

            while ((line = file.ReadLine()) != null)

            {

                txtfile[count] = line;

                textBox1.Text = txtfile[count]+Environment.NewLine;

                count++;

            }

            file.Close();