This guide explains how to include and use a custom_main.js file in your Electron.NET application for advanced Electron/Node.js customization.

• Register custom protocol handlers (e.g., myapp://) — protocols must be registered before the app is fully initialized
• Integrate Node.js modules (e.g., telemetry, OS APIs)
• Control startup logic (abort, environment checks)
• Set up IPC messaging or preload scripts

Place your custom logic in electron/custom_main.js:

module.exports.onStartup = function(host) {
    // Example: Register a global shortcut for opening dev tools
    const { app, globalShortcut, BrowserWindow } = require('electron');
    app.on('ready', () => {
        const ret = globalShortcut.register('Control+Shift+I', () => {
            BrowserWindow.getAllWindows().forEach(win => win.webContents.openDevTools());
            console.log('Ctrl+Shift+I is pressed: DevTools opened!');
        });
    });
    app.on('will-quit', () => {
        globalShortcut.unregisterAll();
    });
    return true;
};

Add this to your .csproj file:

<ItemGroup>
  <None Update="electron\custom_main.js">
    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    <TargetPath>.electron\custom_main.js</TargetPath>
  </None>
</ItemGroup>

Use the standard build/run commands:

dotnet build
dotnet run

Electron.NET will automatically load and execute your custom_main.js before initializing the .NET backend.

Use environment variables to control features:

const env = process.env.ASPNETCORE_ENVIRONMENT || 'Production';
if (env === 'Development') { /* enable dev features */ }

• custom_main.js must use CommonJS syntax (module.exports.onStartup = ...).
• Place the file in your source directory and copy it to .electron using .csproj.
• Electron.NET will abort startup if onStartup returns false.