Question

 DirectoryInfo dir=new DirectoryInfo(path);
 if (!dir.Exists)
  {
      Directory.CreateDirectory(path);
      File.Create(path + "\\file.xml");

      StreamWriter sw =new StreamWriter(path + "\\file.xml");
      sw.Flush();
      sw.Write("<?xml version='1.0' encoding='utf-8' ?><project></project>");
  }

error:

The process cannot access the file ‘C:\file.xml’ because it is being
used by another process.

why? How can close file?

Answer 1

From MSDN

The FileStream object created by this method (File.Create) has a default FileShare value of None; no other process or code can access the created file until the original file handle is closed.

So the workaround is

  using(FileStream fs = File.Create(path + "\\file.xml"))
  {
       Byte[] info = new UTF8Encoding(true).GetBytes("<?xml version='1.0' encoding='utf-8' ?><project></project>");
       fs.Write(info, 0, info.Length);
  }

EDIT: Changed removing the creation of the StreamWriter and using a FileStream
However I don’t like this way as suggested by MSDN.
StreamWriter has a constructor that can get a FileStream, but I thought that if we use

   using(StreamWriter sw = new StreamWriter(File.Create(path + "\\file.xml")))
   { 
      sw.Write("<?xml version='1.0' encoding='utf-8' ?><project></project>");
   }

we get back the locking problem. However, I have tested and it works.
Probably the StreamWriter constructor do some tricks on the FileStream returned by File.Create.