compare byte to byte files using hash alogrithm for getting percentage

private void btnCompare_Click(object sender, EventArgs e)
{
    if(txtFile1.Text != "" && txtFile2.Text !="")
   {
       HashAlgorithm ha = HashAlgorithm.Create();
       FileStream f1 = new FileStream(txtFile1.Text, FileMode.Open);
       FileStream f2 = new FileStream(txtFile2.Text, FileMode.Open);
       /* Calculate Hash */
       byte[] hash1 = ha.ComputeHash(f1);
       byte[] hash2 = ha.ComputeHash(f2);
       f1.Close();
       f2.Close();
       /* Show Hash in TextBoxes */
       txtHash1.Text = BitConverter.ToString(hash1);
       txtHash2.Text = BitConverter.ToString(hash2);
       /* Compare the hash and Show Message box */
       if (txtHash1.Text == txtHash2.Text)
       {
           MessageBox.Show("Files are Equal !");
       }
       else
       {
           MessageBox.Show("Files are Diffrent !");
       }
   }
}
private void btnSelectFile1_Click(object sender, EventArgs e)
{
   OpenFileDialog ofd = new OpenFileDialog();
   if (ofd.ShowDialog() == DialogResult.OK)
   {
        txtFile1.Text = ofd.FileName;
   }
}
private void btnSelectFile2_Click(object sender, EventArgs e)
{
   OpenFileDialog ofd = new OpenFileDialog();
   if (ofd.ShowDialog() == DialogResult.OK)
   {
        txtFile2.Text = ofd.FileName;
   }
}