Help me to compare 2 images with each other.

Question

I have 2 buttons in my Form.
I set the property of Image of 2 buttons load from 1 image in my hardrive.
But I cannot use "==" operator to check whether two images in two buttons is the same??(I knew they are the same)
ex:
             if (button1.Image == button2.Image)    //The images in button1 and button I loaded from the same file!
                MessageBox.Show("the same images");
            else
                MessageBox.Show("different images");

--->They show MessageBox02: different images
Please help me how to compare the property of images in 2 buttons.
Thanks in advance.