protected override void OnInvoke()

in src/Microsoft.VisualStudio.SlowCheetah.VS/Package/PreviewTransformCommand.cs [118:170]
37 lines of code
7 McCabe index (conditional complexity)

        protected override void OnInvoke(object sender, EventArgs e)
        {
            uint itemId = VSConstants.VSITEMID_NIL;

            // Verify only one item is selected
            if (!ProjectUtilities.IsSingleProjectItemSelection(out IVsHierarchy hierarchy, out itemId))
            {
                return;
            }

            // Make sure that the project supports transformations
            IVsProject project = (IVsProject)hierarchy;
            if (!this.ScPackage.ProjectSupportsTransforms(project))
            {
                return;
            }

            // Get the full path of the selected file
            if (ErrorHandler.Failed(project.GetMkDocument(itemId, out string transformPath)))
            {
                return;
            }

            // Checks the SlowCheetah NuGet package installation
            this.ScPackage.JoinableTaskFactory.Run(() => this.NuGetManager.CheckSlowCheetahInstallation(hierarchy));

            // Get the parent of the file to start searching for the source file
            ErrorHandler.ThrowOnFailure(hierarchy.GetProperty(itemId, (int)__VSHPROPID.VSHPROPID_Parent, out object parentIdObj));
            uint parentId = (uint)(int)parentIdObj;
            if (parentId == (uint)VSConstants.VSITEMID.Nil)
            {
                return;
            }

            if (!this.TryGetFileToTransform(hierarchy, parentId, Path.GetFileName(transformPath), out uint docId, out string documentPath))
            {
                throw new FileNotFoundException(string.Format(CultureInfo.CurrentCulture, Resources.Resources.Error_FileToTransformNotFound, transformPath));
            }

            try
            {
                // Save the source and transform files before previewing
                PackageUtilities.GetAutomationFromHierarchy<ProjectItem>(hierarchy, docId).Save();
                PackageUtilities.GetAutomationFromHierarchy<ProjectItem>(hierarchy, itemId).Save();
            }
            catch
            {
                // If the item is not open, an exception is thrown,
                // but that is not a problem as it is not dirty
            }

            this.PreviewTransform(hierarchy, documentPath, transformPath);
        }