实现效果:

知识运用:
PictureBox控件的MouseEnter事件
窗体的MouseMove事件
实现代码:
bool flag=false;
private void pictureBox1_MouseEnter(object sender, EventArgs e)
{
flag = true;
}
private void Form1_MouseMove(object sender, MouseEventArgs e)
{
if (flag)
pictureBox1.Location = new System.Drawing.Point(e.X,e.Y);
}