初学C#，写了段代码，在Form1  load时动态添加一个textBox控件和Button控件，然后在Button控件单击事件中用到textBox的text属性，下面是代码，

private void Form1_Load(object sender, EventArgs e)
        {
            TextBox txbox = new TextBox();
            txbox.Name = "textBox1";
            txbox.Text = "aaa";
            txbox.Location = new Point(15,15);
            txbox.Size = new Size(150,20);
            this.Controls.Add(txbox);

            Button btn = new Button();
            btn.Text = "sure";
            btn.Location = new Point(165,15);
            btn.Size = new Size(60,20);
            btn.Click += new EventHandler(btn_Click);
            this.Controls.Add(btn);
        }
        void btn_Click(object senedr, EventArgs e)
        {
            MessageBox.Show(txbox.text);
        }

编译时提示： Error    1    The name 'txbox' does not exist in the current context    d:\ 我的文档\Visual Studio 2005\Mytest\Mytest\test\Form1.cs    36    29    test

不知道怎么回事啊，怎么找不到textBox控件呢！！！