excel

Excel COM Add-in with DotNetBrowser

This example shows how to build a .NET Framework COM add-in that embeds DotNetBrowser in an Excel task pane and lets a web page read and write spreadsheet data through a JavaScript bridge.

Prerequisites

• Windows
• .NET Framework 4.7.2
• Microsoft Excel
• A DotNetBrowser license key

Project structure

• AddIn/Connect.cs is the COM entry point Excel loads at startup. It implements the add-in lifecycle, supplies the ribbon XML, and creates the task pane.
• AddIn/ComRegistration.cs writes and removes the registry keys that register the add-in with Excel.
• Interop/ComConstants.cs holds the ProgId and GUID that identify the COM class.
• Ribbon/RibbonController.cs owns the ribbon XML and handles the "Open Panel" button callback.
• Browser/EngineManager.cs creates the DotNetBrowser engine and registers the app:// scheme used to serve the bundled web page.
• TaskPane/BrowserHostControl.cs is the COM-visible WinForms control that hosts the browser inside the task pane. It exposes readFromExcel and writeToExcel to JavaScript as window.excelBridge.
• TaskPane/TaskPaneManager.cs coordinates the task pane and engine lifecycle and implements the Excel cell read/write logic.
• Web/index.html is the web UI bundled with the add-in.

Set the license key

Open Browser/EngineManager.cs and set your license key:

var builder = new EngineOptions.Builder
{
    LicenseKey = "<your_license_key>",
    ...
};

Build and register

Build the project with MSBuild:

msbuild src/ExcelComAddin/ExcelComAddin.csproj /p:Configuration=Debug

Or open ExcelComAddin.sln in Visual Studio and build from there.

Then register the add-in using the provided script (requires an elevated PowerShell prompt):

.\scripts\com-registration.ps1 -Action register

To unregister:

.\scripts\com-registration.ps1 -Action unregister

To check the current registration status without making any changes:

.\scripts\com-registration.ps1 -Action status

If you use Visual Studio, you can alternatively enable Register for COM Interop in Project Properties → Build for the Debug configuration and the registration will run automatically on each build.

Run the example

After a successful build, open Excel. A Sales Lead Add-in tab appears in the ribbon. Click Open Panel to open the task pane with the browser UI loaded.

• Click Read from Excel to display the current value of cell A1.
• Type a value and click Write to Excel to write it directly to the cell.