我怎样才能改变图片框的背景色，数字将从文本框中取出

private PictureBox[] picturebox = new PictureBox[64];
private void button2_Click(object sender, EventArgs e)
{         
   int i = int.Parse(textBox1.Text);             
   picturebox[i].BackColor = Color.Green;
}

当按钮点击时，我将从用户获取1到64之间的数字，我将改变用户想要的图片框的背景色。

为例:

int i=3;
pictureBox3.BackColor=color.green;

int i = 3;
string PB= "pictureBox" + i;
PictureBox pb= this.Controls.Find(PB, true).FirstOrDefault() as PictureBox;
pb.BackColor = Color.Green;