public bool CreateAndLoadBuffer()
        {
            DestroyBuffer();

            var pkg = PackageManager.Package as Package;
            IServiceProvider serviceProvider = pkg;

            var textLinesType = typeof(VSTextManagerInterop.IVsTextLines);
            var riid = textLinesType.GUID;
            var clsid = typeof(VSTextManagerInterop.VsTextBufferClass).GUID;

            _underlyingBuffer = pkg.CreateInstance(ref clsid, ref riid, textLinesType);
            Debug.Assert(_underlyingBuffer != null, "Failure while creating buffer.");

            var buffer = _underlyingBuffer as VSTextManagerInterop.IVsTextLines;
            Debug.Assert(buffer != null, "Why does buffer not implement IVsTextLines?");

            var ows = buffer as IObjectWithSite;
            if (ows != null)
            {
                ows.SetSite(serviceProvider.GetService(typeof(IOleServiceProvider)));
            }

            // We want to set the LanguageService SID explicitly to the XML Language Service.
            // We need turn off GUID_VsBufferDetectLangSID before calling LoadDocData so that the 
            // TextBuffer does not do the work to detect the LanguageService SID from the file extension.
            var userData = buffer as VSTextManagerInterop.IVsUserData;
            if (userData != null)
            {
                var VsBufferDetectLangSID = new Guid("{17F375AC-C814-11d1-88AD-0000F87579D2}"); //GUID_VsBufferDetectLangSID;
                VSErrorHandler.ThrowOnFailure(userData.SetData(ref VsBufferDetectLangSID, false));
            }

            var langSid = CommonPackageConstants.xmlEditorLanguageService;
            VSErrorHandler.ThrowOnFailure(buffer.SetLanguageServiceID(ref langSid));

            var persistDocData = buffer as IVsPersistDocData;
            if (persistDocData != null)
            {
                persistDocData.LoadDocData(FileName);
                var artifactUri = new Uri(FileName);

                var artifact = PackageManager.Package.ModelManager.GetArtifact(artifactUri);
                if (artifact != null
                    && artifact.IsCodeGenArtifact)
                {
                    var standaloneProvider = artifact.XmlModelProvider as StandaloneXmlModelProvider;
                    if (standaloneProvider.ExtensionErrors == null
                        || standaloneProvider.ExtensionErrors.Count == 0)
                    {
                        // If there is a cached code gen artifact, it will have loaded its text buffer using extensions already.
                        // Therefore we can grab the text buffer from that artifact for our docdata buffer, and dispose the
                        // code gen artifact since it's using a XmlProvider that is standalone and won't be supported by the
                        // designer.
                        var projectItem = VsUtils.GetProjectItem(Hierarchy, ItemId);
                        if (projectItem != null)
                        {
                            if (VSHelpers.CheckOutFilesIfEditable(ServiceProvider, new[] { FileName }))
                            {
                                string artifactText = null;
                                using (var writer = new Utf8StringWriter())
                                {
                                    artifact.XDocument.Save(writer, SaveOptions.None);
                                    artifactText = writer.ToString();
                                }

                                if (!String.IsNullOrWhiteSpace(artifactText))
                                {
                                    VsUtils.SetTextForVsTextLines(VsBuffer, artifactText);
                                }
                            }
                            else
                            {
                                ErrorListHelper.LogExtensionErrors(
                                    new List<ExtensionError>
                                        {
                                            new ExtensionError(
                                                string.Format(
                                                    CultureInfo.CurrentCulture, Resources.ExtensionError_SourceControlLock,
                                                    Path.GetFileName(FileName)),
                                                ErrorCodes.ExtensionsError_BufferNotEditable,
                                                ExtensionErrorSeverity.Error)
                                        },
                                    projectItem);
                            }
                        }

                        PackageManager.Package.ModelManager.ClearArtifact(artifactUri);
                    }
                    else
                    {
                        // If the extensions ran into errors whilst loading, we'll need to re-run extensions anyway so we ignore the cache
                        PackageManager.Package.ModelManager.ClearArtifact(artifactUri);
                        DispatchLoadToExtensions();
                    }
                }
                else
                {
                    DispatchLoadToExtensions();
                }
            }

            // DSL exposes the FileNameChanged event which we subscribe to so we can update the moniker inside
            // the text buffer, which is required to update our model as well as keep the XmlModel in sync.
            FileNameChanged += OnFileNameChanged;
            RegisterUndoTracking();
            return true;
        }
        internal string DispatchSaveToExtensions(
            IServiceProvider serviceProvider, ProjectItem projectItem, string fileContents,
            Lazy<IModelConversionExtension, IEntityDesignerConversionData>[] converters,
            Lazy<IModelTransformExtension>[] serializers)
        {
            Debug.Assert(projectItem != null, "projectItem != null");
            Debug.Assert(fileContents != null, "bufferText != null");
            Debug.Assert(serializers != null && converters != null, "extensions must not be null");
            Debug.Assert(serializers.Any() || converters.Any(), "at least one extension expected");

            ModelTransformContextImpl transformContext = null;
            ModelConversionContextImpl conversionContext = null;

            try
            {
                var original = XDocument.Parse(fileContents, LoadOptions.PreserveWhitespace);
                var targetSchemaVersion = EdmUtils.GetEntityFrameworkVersion(projectItem.ContainingProject, serviceProvider);
                Debug.Assert(targetSchemaVersion != null, "we should not get here for Misc projects");

                transformContext = new ModelTransformContextImpl(projectItem, targetSchemaVersion, original);

                // call the extensions that can save EDMX files first (even if we aren't going to end up in an EDMX file, let them process)
                VSArtifact.DispatchToSerializationExtensions(serializers, transformContext, loading: false);

                // get the extension of the file being loaded (might not be EDMX); this API will include the preceeding "."
                var fileInfo = new FileInfo(FileName);
                var fileExtension = fileInfo.Extension;

                // now if this is not an EDMX file, hand off to the extension who can convert it to the writable content
                if (!string.Equals(fileExtension, EntityDesignArtifact.ExtensionEdmx, StringComparison.OrdinalIgnoreCase))
                {
                    // the current document coming from the serializers becomes our original
                    conversionContext = new ModelConversionContextImpl(
                        projectItem.ContainingProject, projectItem, fileInfo, targetSchemaVersion, transformContext.CurrentDocument);

                    // we aren't loading an EDMX file, so call the extensions who can process this file extension
                    // when this finishes, then output should be a valid EDMX document
                    VSArtifact.DispatchToConversionExtensions(converters, fileExtension, conversionContext, false);

                    // we are done saving, so get bufferText from the OriginalDocument
                    // TODO use Utf8StringWriter here somehow?
                    return conversionContext.OriginalDocument;
                }
                else
                {
                    // we are saving an EDMX file, so get bufferText from the XDocument
                    using (var writer = new Utf8StringWriter())
                    {
                        transformContext.CurrentDocument.Save(writer, SaveOptions.None);
                        return writer.ToString();
                    }
                }
            }
            catch (XmlException)
            {
                // Don't do anything here. We will want to gracefully step out of the extension loading
                // and let the core designer handle this.
                return fileContents;
            }
            finally
            {
                var errorList = ErrorListHelper.GetExtensionErrorList(serviceProvider);
                errorList.Clear();

                // log any errors
                if (conversionContext != null)
                {
                    if (conversionContext.Errors.Count > 0)
                    {
                        ErrorListHelper.LogExtensionErrors(conversionContext.Errors, projectItem);
                    }
                    conversionContext.Dispose();
                }

                if (transformContext != null)
                {
                    if (transformContext.Errors.Count > 0)
                    {
                        ErrorListHelper.LogExtensionErrors(transformContext.Errors, projectItem);
                    }
                    transformContext.Dispose();
                }
            }
        }
        internal static bool TryGetBufferViaExtensions(
            IServiceProvider serviceProvider, ProjectItem projectItem, string fileContents,
            Lazy<IModelConversionExtension, IEntityDesignerConversionData>[] converters,
            Lazy<IModelTransformExtension>[] serializers, out string documentViaExtensions,
            out List<ExtensionError> errors)
        {
            Debug.Assert(serviceProvider != null, "serviceProvider != null");
            Debug.Assert(projectItem != null, "projectItem != null");
            Debug.Assert(VsUtils.EntityFrameworkSupportedInProject(projectItem.ContainingProject, serviceProvider, false));
            Debug.Assert(serializers != null && converters != null, "extensions must not be null");
            Debug.Assert(serializers.Any() || converters.Any(), "at least one extension expected");

            errors = new List<ExtensionError>();
            documentViaExtensions = "";

            ModelConversionContextImpl conversionContext = null;
            ModelTransformContextImpl transformContext = null;

            try
            {
                var targetSchemaVersion =
                    EdmUtils.GetEntityFrameworkVersion(projectItem.ContainingProject, serviceProvider);

                Debug.Assert(targetSchemaVersion != null, "should not get here for a Misc project");

                // get the extension of the file being loaded (might not be EDMX); this API will include the preceeding "."
                var filePath = projectItem.get_FileNames(1);
                var fileExtension = Path.GetExtension(filePath);
                XDocument originalDocument = null;

                // see if we are loading an EDMX file or not, and if we have any converters
                if (!string.Equals(
                    fileExtension, EntityDesignArtifact.ExtensionEdmx,
                    StringComparison.OrdinalIgnoreCase))
                {
                    conversionContext = new ModelConversionContextImpl(
                        projectItem.ContainingProject, projectItem, new FileInfo(filePath),
                        targetSchemaVersion, fileContents);

                    // we aren't loading an EDMX file, so call the extensions who can process this file extension
                    // when this finishes, then output should be a valid EDMX document
                    VSArtifact.DispatchToConversionExtensions(converters, fileExtension, conversionContext, true);

                    // we are done with the non-EDMX extensions so CurrentDocument will be a valid EDMX document
                    // create the serialization context for further extensions to act on
                    transformContext = new ModelTransformContextImpl(
                        projectItem, targetSchemaVersion, conversionContext.CurrentDocument);
                }
                else
                {
                    // we are loading an EDMX file, we can parse file contents into an XDocument
                    try
                    {
                        originalDocument = XDocument.Parse(fileContents, LoadOptions.PreserveWhitespace);
                        transformContext = new ModelTransformContextImpl(
                            projectItem, targetSchemaVersion, originalDocument);
                    }
                    catch (XmlException)
                    {
                        // If there's an error here, don't do anything. We will want to gracefully step out of the extension loading
                        // since the designer itself won't load.
                    }
                }

                if (transformContext != null
                    && originalDocument != null)
                {
                    // now dispatch to those that want to work on EDMX files
                    VSArtifact.DispatchToSerializationExtensions(serializers, transformContext, true);

                    // TODO: this does not seem to be correct if severity is Message or Warning
                    if (transformContext.Errors.Count == 0)
                    {
                        // see if any extension changed things. Note that we need to compare the serialization of
                        // the XDocuments together since the original buffer may have different whitespace after creating the XDocument.
                        // TODO: Why not use XNode.DeepEquals()?
                        string newBufferContents;
                        using (var currentDocWriter = new Utf8StringWriter())
                        {
                            transformContext.CurrentDocument.Save(currentDocWriter, SaveOptions.None);
                            newBufferContents = currentDocWriter.ToString();
                        }

                        string originalBufferContents;
                        using (var originalDocWriter = new Utf8StringWriter())
                        {
                            originalDocument.Save(originalDocWriter, SaveOptions.None);
                            originalBufferContents = originalDocWriter.ToString();
                        }

                        if (!string.Equals(originalBufferContents, newBufferContents, StringComparison.Ordinal))
                        {
                            documentViaExtensions = newBufferContents;
                            return true;
                        }
                    }
                    else
                    {
                        errors.AddRange(transformContext.Errors);
                        return false;
                    }
                }
            }
            finally
            {
                var errorList = ErrorListHelper.GetExtensionErrorList(serviceProvider);
                errorList.Clear();

                // log any errors                   
                if (conversionContext != null
                    && conversionContext.Errors.Count > 0)
                {
                    ErrorListHelper.LogExtensionErrors(conversionContext.Errors, projectItem);
                }

                if (transformContext != null
                    && transformContext.Errors.Count > 0)
                {
                    ErrorListHelper.LogExtensionErrors(transformContext.Errors, projectItem);
                }
            }

            return false;
        }