Solving the MS365 Word Add-in Conundrum: Search for Text Ranges Throws InteropServices.COMException (0x800A16C9)

Welcome to the world of MS365 Word Add-in development, where the impossible becomes possible, and the possible becomes an exercise in frustration. Today, we’re going to tackle one of the most vexing errors you’ll encounter: the infamous InteropServices.COMException (0x800A16C9) – “An error occurred while saving the undo information” when searching for text ranges.

The Problem: Searching for Text Ranges Gone Wrong

Imagine you’ve lovingly crafted an MS365 Word Add-in to revolutionize the way users interact with Microsoft Word. It’s a masterpiece of coding wizardry, complete with sleek UI elements and seamless integration with Word’s core functionality. But, as you proudly demonstrate your creation to your colleagues, disaster strikes. Your Add-in’s search function, which should effortlessly traverse the document’s text ranges, suddenly coughs up an InteropServices.COMException (0x800A16C9) like a digital hairball.

The error message, “An error occurred while saving the undo information,” is about as helpful as a chocolate teapot. It’s a cryptic message that leaves you scratching your head, wondering what dark sorcery has afflicted your code.

The Culprit: Word’s Undo Management

To unravel the mystery, we need to delve into the inner workings of Word’s Undo management. When your Add-in searches for text ranges, it modifies the document’s content, which triggers Word’s Undo system to save the changes. This is where the problem lies. Word’s Undo management is a delicate dance of COM interfaces, and any misstep can result in the dreaded InteropServices.COMException.

COM and the Word Object Model

COM (Component Object Model) is a binary interface standard developed by Microsoft for inter-process communication. In the context of Word, COM enables your Add-in to interact with the Word Object Model, allowing you to manipulate documents, paragraphs, and text ranges. However, this interaction also opens the door to potential compatibility issues and errors.

The Solution: Taming the Undo Beast

Fear not, dear developer, for we’ve got a comprehensive solution to tame the Undo beast and banish the InteropServices.COMException (0x800A16C9). Follow these steps to ensure your search function works harmoniously with Word’s Undo management:

Step 1: Disable Undo Recording

Before searching for text ranges, disable Undo recording using the Application.UndoRecording property. This prevents Word from saving undo information, which is the root cause of the error.

using Microsoft.Office.Tools.Word;

// Disable Undo recording
Application app = Globals.ThisAddIn.Application;
app.UndoRecording = false;

Step 2: Perform Your Search

With Undo recording disabled, perform your search function as usual. This can include using the Word.Range object to search for specific text or patterns.

using Microsoft.Office.Interop.Word;

// Create a range object for the entire document
Range range = app.ActiveDocument.Content;

// Perform your search logic here
string searchText = "Hello, World!";
range.Find.ClearFormatting();
range.Find.Text = searchText;

// Execute the search
bool found = range.Find.Execute();

// Process the search results as needed
if (found)
{
    // Do something with the found text range
}

Step 3: Re-enable Undo Recording

After completing your search, re-enable Undo recording to allow Word to resume saving undo information.

// Re-enable Undo recording
app.UndoRecording = true;

Step 4: Clean Up (Optional)

If your search function modifies the document’s content, consider cleaning up any unnecessary undo steps using the Application.UndoClear() method. This ensures that the user’s Undo history is not polluted with unnecessary entries.

// Clean up undo steps (optional)
app.UndoClear();

Conclusion: Subduing the InteropServices.COMException

By following these steps, you’ve successfully tamed the Undo beast and banished the InteropServices.COMException (0x800A16C9) from your MS365 Word Add-in. Remember to disable and re-enable Undo recording, perform your search function, and clean up any unnecessary undo steps. With these best practices in place, your Add-in will work in harmony with Word’s Undo management, ensuring a seamless user experience.

Additional Tips and Resources

• When working with COM objects, ensure you properly release any resources using the Marshal.ReleaseComObject() method to avoid memory leaks.
• For more information on Word’s Undo management, refer to the Microsoft Office Dev Center documentation on Application.UndoRecording.
• For comprehensive guidance on building MS365 Word Add-ins, explore the Microsoft Office Add-ins documentation.

Common Error Codes	Description
0x800A16C9	“An error occurred while saving the undo information”
0x800401A8	“The operation cannot be completed because the document is not in the correct state”
0x80040454	“The Undo stack is empty or corrupted”

Now, go forth and conquer the world of MS365 Word Add-in development! With this guide, you’re well-equipped to tackle the most daunting errors and create innovative solutions that delight your users.

Frequently Asked Question

Have you ever encountered the frustrating error “An error occurred while saving the undo information” while searching for text ranges in MS365 Word Add-in? Worry no more! We’ve got you covered.