Passing a query string value retrieved to an ImageUrl attribute of an image control using asp.net c#

Question

I have a page called DisplayImage and within the page_load event i was able to retrieve some
values from the query string
hcode=Request.Querystring["ccode"].Tostring();
Now,
hcode="6699FD";
However i want to pass the value of  6699FD to another page to run a process and return a byte image
<asp:Image ID="img1" runat="server" ImageUrl="~/RetrieveImage.aspx?ID=" 6699FD  />
 
How can I pass the value of  6699FD as a parameter to my Imageurl so that i can use it to retrieve my image.