btn2'在当前上下文中不存在

下面我放了一些代码的问题是btn2.tag。它说"名称'btn2'在当前上下文中不存在"，我如何解决这个问题?这条路是什么?

    public Main()
    {
        InitializeComponent();
        // bla bla bla
        int NumOfButtons = 12;
        int loc = 20; 
        int k = 5;
        for (int i = 1; i <= NumOfButtons; i++)
        {
            Button btn = new Button();
            {
                lst.Location = new Point(4, 4);
                btn.Size = new Size(55, 55);
                btn.Tag = i;
                command.CommandText = "select product_Name from T_Product where PRODUCT_ID = " + btn.Tag;
                btn.Text = command.ExecuteScalar().ToString();  
                btn.Location = new Point(k, loc);
            }

            btn.Click += Buttons_Click;  
    }
    private void Buttons_Click(System.Object sender, System.EventArgs e)
    {
        isclicked = true;
        // Used "Sender" to know which button was clicked ?
        Button btn = sender as Button;
        Button btn2 = sender as Button;
        btn2.Tag = btn.Tag;

    }
    private void button5_Click(object sender, EventArgs e)
    {
        if (textBox1.Text != "")
        {
            SqlConnection conn = new SqlConnection(@"server=.'SQLEXPRESS;Initial Catalog=DUK1;Integrated Security=True;Pooling=False");
            command.Connection = conn;
            conn.Open();      
            command.CommandText = "select product_PRIZE from T_Product where PRODUCT_ID = " + btn2.Tag;   // here problem occurs
            textBox5.Text = comando.ExecuteScalar().ToString();
        }

}

//////

在这个例子中我有一些按钮(12)，当我点击button5和button5时，我想根据btn2显示奖品。标签(这是12个按钮的标签之一)。