How to show the hex values that have been read from a file on a label or text box?

Question

When using the BinaryReader, i can read the files though I'm currently having issues showing the hex values that have been read from the offsets or parameters that i have set in the for-loop

OpenFileDialog ofd = new OpenFileDialog();

private void btnValue_Click(object sender, EventArgs e)
{

    ofd.ShowDialog();

    BinaryReader br = new BinaryReader(File.OpenRead(ofd.FileName));

    String value = null;
    for (int i = 0x28; i <= 0x35; i++)
    {
        br.BaseStream.Position = i;
        value += br.ReadByte().ToString("X2");

    }

    br.Close();

    lblValue.Text = Value;
}

the values that I want to show should be in hex format "FF3D0EC1".