need C# code for following problem

Question

I wanted to load contents of text files by using button to richtextbox.It is working for english language file but when I was looking for bengali text file its not working....i am giving my codes below..please help me..

 

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.IO;

using System.Linq;

using System.Text;

using System.Windows.Forms;

//using itextsharp.text;

//using iTextsharp.text.pdf;

//using iTextsharp.text.pdf.parser;

namespace tokenizer

{

public partial class Form1 : Form

{

public Form1()

{

InitializeComponent();

}

private void button1_Click(object sender, EventArgs e)

{

Stream Mystream;

OpenFileDialog openfiledialog1 = new OpenFileDialog();

if (openfiledialog1.ShowDialog() == System.Windows.Forms.DialogResult.OK)

{

if ((Mystream = openfiledialog1.OpenFile()) != null)

{

string strfilname = openfiledialog1.FileName;

string filetext = File.ReadAllText(strfilname);

richTextBox1.Text = filetext;

}

}

}

}

}