How to insert Calender control in asp.net

Question

I have a panel. in that panel there is one text box for some input and another one for taking date from calender control. i have put calender control below the second text box(i.e. txtDate), but i dont want it to be displayed when the page is loaded,instead  i want a small image of calender and on clicking that image a calender should pop up and selected date must be captured by txtdate textbox.
Please help me with .aspx and .cs file.
I m using asp.net with C#.