How To Implement a Windows Live Writer Plug-in That Checks For Missing Tags

This post provides the technical details on how I’ve implemented the Windows Live Writer Plug-in Check For Missing Tags, which was presented here.

What Is This Plug-in Anyway?

This plug-in will remind you to add the proper tags if they are missing.

Trying to post without proper tagging when the plug-in is installed will result with the following dialog:

Clicking on the Cancel button (which is the default) will abort the publish operation and will let you update the categories.

The list of required categories is saved in a simple text file (required_categories.txt) next to the plug-in dll.

How It Was Built?

Following are the full instruction on how to build such a plug-in.
You can find the full source here.

1. Create new class library project named CheckMissingTagsPlugin. Make sure you use .NET framework 3.5 since .NET 4 plugins are not supported.
   
2. Add reference to WindowsLive.Writer.Api, located in C:\Program Files\Windows Live\Writer.
   
3. Add reference to System.Windows.Forms, located in the GAC.
   
4. Create a class named CheckMissingTags that inherits from PublishNotificationHook.
   
5. Apply attribute WriterPluginAttribute to the class.
   
   
   [WriterPlugin("EF0CAF97-12C2-4446-BDC4-19EE53781351", "Check For Missing Tags")]
   public class CheckMissingTags : PublishNotificationHook
   {
   
   }
   
   
6. Override the method OnPrePublish. Here we can check for missing categories and notify the user.
   
   
   
   public override bool OnPrePublish(IWin32Window dialogOwner, IProperties properties, IPublishingContext publishingContext, bool publish)
   {
       // get list of required categories
       string[] requiredCategories;
       if (File.Exists(FileName))
       {
           requiredCategories = File.ReadAllLines(FileName);
       }
       else
       {
           // warn about missing required categories
           string message =
               "Missing categories file: " + FileName + "\n" +
               "Post anyway?";
   
           DialogResult dialogResult = MessageBox.Show(
               dialogOwner,
               message,
               "Warning",
               MessageBoxButtons.OKCancel,
               MessageBoxIcon.Warning,
               MessageBoxDefaultButton.Button2);
   
           // allow post only if user selected OK
           return dialogResult == DialogResult.OK;
       }
   
       // get list of available categories
       IEnumerable<string> availableCategories =
           from category in publishingContext.PostInfo.Categories
           select category.Name;
   
       // is one of the required categories available?
       bool hasAnyRequestedCategory = availableCategories.Any(
           s => requiredCategories.Contains(s, StringComparer.OrdinalIgnoreCase));
   
       if (!hasAnyRequestedCategory)
       {
           string allRequiredCategories = string.Join(", ", requiredCategories);
           string message =
               "None of the required categories are available.\n" +
               "(" + allRequiredCategories + ")\n" +
               "Post without required categories?";
   
           // warn about missing required categories
           DialogResult dialogResult = MessageBox.Show(
               dialogOwner,
               message,
               "Warning",
               MessageBoxButtons.OKCancel,
               MessageBoxIcon.Warning,
               MessageBoxDefaultButton.Button2);
   
           // allow post only if user selected OK
           return dialogResult == DialogResult.OK;
       }
   
       return true;
   }
   
   
7. Add the following line to the post build event:
   
   XCOPY /D /Y /R "$(TargetPath)" "%ProgramFiles%\Windows Live\Writer\Plugins\"
   
8. Build project.

Note: In order for the post build event to work you need to run Visual Studio as Administrator.

That’s it for now,
Arik Poznanski.