Microsoft.VisualStudio.Project.SingleFileGenerator.UpdateGeneratedCodeFile C# (CSharp) Method

        protected virtual string UpdateGeneratedCodeFile(FileNode fileNode, byte[] data, int size, string fileName)
        {
            if (fileNode == null)
                throw new ArgumentNullException("fileNode");
            if (data == null)
                throw new ArgumentNullException("data");

            string filePath = Path.Combine(Path.GetDirectoryName(fileNode.GetMKDocument()), fileName);
            IVsRunningDocumentTable rdt = this.projectMgr.GetService(typeof(SVsRunningDocumentTable)) as IVsRunningDocumentTable;

            // (kberes) Shouldn't this be an InvalidOperationException instead with some not to annoying errormessage to the user?
            if(rdt == null)
            {
                ErrorHandler.ThrowOnFailure(VSConstants.E_FAIL);
            }

            IVsHierarchy hier;
            uint cookie;
            uint itemid;
            IntPtr docData = IntPtr.Zero;
            ErrorHandler.ThrowOnFailure(rdt.FindAndLockDocument((uint)(_VSRDTFLAGS.RDT_NoLock), filePath, out hier, out itemid, out docData, out cookie));
            if(docData != IntPtr.Zero)
            {
                Marshal.Release(docData);
                IVsTextStream srpStream = null;
                if(srpStream != null)
                {
                    int oldLen = 0;
                    int hr = srpStream.GetSize(out oldLen);
                    if(ErrorHandler.Succeeded(hr))
                    {
                        IntPtr dest = IntPtr.Zero;
                        try
                        {
                            dest = Marshal.AllocCoTaskMem(data.Length);
                            Marshal.Copy(data, 0, dest, data.Length);
                            ErrorHandler.ThrowOnFailure(srpStream.ReplaceStream(0, oldLen, dest, size / 2));
                        }
                        finally
                        {
                            if(dest != IntPtr.Zero)
                            {
                                Marshal.Release(dest);
                            }
                        }
                    }
                }
            }
            else
            {
                using(FileStream generatedFileStream = File.Open(filePath, FileMode.OpenOrCreate))
                {
                    generatedFileStream.Write(data, 0, size);
                }

                EnvDTE.ProjectItem projectItem = fileNode.GetAutomationObject() as EnvDTE.ProjectItem;
                if(projectItem != null && (this.projectMgr.FindChild(fileNode.FileName) == null))
                {
                    projectItem.ProjectItems.AddFromFile(filePath);
                }
            }
            return filePath;
        }