File.Create(string path)
Creates a file and leaves the stream open.
you need to do the following:
Directory.CreateDirectory(dstPath);
File.Copy(srcPath + "\\File1.txt", dstPath + "\\File1.txt");
using (var stream = File.Create(dstPath + "\\" + "File2.txt"))
{
//you can write to the file here
}
The using statement asures you that the stream will be closed and the lock to the file will be released.
Hope this helps