asp:DataList ID="DataList1" runat="server" RepeatDirection="Horizontal" RepeatColumns="5"
CellSpacing="25">
ItemTemplate>
img src="%# Eval("FullName") %>" width="50" height="50" border="0" >
/ItemTemplate>
/asp:DataList>

string path = Server.MapPath("img");//获取img文件夹的路径
Response.Write(path);
DirectoryInfo di = new DirectoryInfo(path);
//DataList1.DataSource = di.GetFiles("*.jpg");只获取jpg图片
DataList1.DataSource = di.GetFiles();//获取文件夹下所有的文件
DataList1.DataBind();