error to save xml

When I call:

doc1.Save("C:\\Users\\Man开发者_开发问答sour\\Documents\\Visual Studio
  2008\\WebSites\\WebSite1\\Web.sitemap");

I get the following error. What does this error mean?

The process cannot access the file 'C:\Users\Mansour\Documents\Visual Studio 2008
  \WebSites\WebSite1\Web.sitemap' because it is being used by another process.

It means that another program has the file open and is locking it. You can use a tool like FileMon to tell you what program is causing the problem.