when i right click the object, and select "go to definition", VS said that " a definition for the symbol 'XXXX' could not be located", here 'XXX' is the name of the object which i right clicked on.
i don't know why this happened. But when i get the previos version of XX.sln file, this didn't happen. that is, the problem is not because of Visual Studio 2010, but because of my XX.sln file.
i tried to figure out what had been done to the XX.sln file, except for two projects, nothing else had been changed. So I got the latest version of XX.sln, removed the two projects, and then reopen the XX.sln file, all worked correctly. and I got latest XX.sln from the version control system again, Visual studio 2010 reloaded all the projects, and nothing strange happened again. everything worked correctly.
how strange thing it it!