Hi,
Thanks for help.
After read your reply, I recreated a new peoject with standard template, I added a feautelayer as the following:
<esri:FeatureLayer ID="FLayer" > </esri:FeatureLayer>
Now, I could compile successfully, but when I tried to run, the map could not be dispalyed, IE browser show: Error on page. I did the same on my working app which created with show case template, it was the same.
As soon as I removed or set a default URL for Featurelayer in .xaml , everything was OK.
I forgot what exactly error meesage showed before, since it was a few week ago. it seems something like: the tag already declared in app.xaml. But as I tested now, as long as I set a default URL in .xaml, it was Ok, no error.
I don't know what is wrong? now, I am using Graphicslayer instead for my purpose, but if I can fix the problem , use the featurelayer, it will help me a lot.
Thanks again.