Avoid Image getting stretched when displaying in ASP.Net Image Control

Hi

i have image tag in datalist  that width=100px  Hight=100px

and I have several image in my database with different size

img1=100*100    img2=500*600    img3=150*140 and ...

now whene i bind my image tag from database it show all my image but it stretch all image.

eg:if my image be  300*500  when it show in image tag it stretch my image from width .

i want if my image size be reduceو it reduce width&Hight  deppending to real size of image don't stretch it.

best regards