C#如何通过单击combox控件里的选项来更改picturebox控件的图片

C#如何通过单击combox控件里的选项来更改picturebox控件的图片如下图形式，这是别人的程序，我自己不会做这样的

编程新手，请大神指点！最好写出代码

private void Form1_Load(object sender, EventArgs e)
        {
            comboBox1.DropDownStyle = ComboBoxStyle.DropDownList;
            string[] str = new string[] { "单相双柱式", "三相三柱式", "三相五柱式", "单相单柱旁轭式", "三相壳式", "单相卷铁心式", "三相平面式卷铁心", "单相双柱旁轭式铁心" };
            comboBox1.DataSource = str;
            comboBox1.SelectedIndex = 0;
        }
 private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {

        }