Change image In Gridview

Question

hi ,
 
i want to know how i can change the image in gridview based on DataRow Value , such as in this forum when you Mark post as answer agreen true image appear !
assume That DataRow row =new DataRow();
 if (row["PostStatus"]=="Answered")
{
change Image
}
if any one also can tell me how to do this in datalist i will be more happy , because i will need it
 
thank u
 
HappyNew year