Office Add-ins Developer

Sisainfosec; Bengaluru; On-site; INR 900,000 - 1,200,000; Full time

Job summary

Sisainfosec is seeking an experienced Office Add-ins Developer to design and build Microsoft Office add-ins using C#, .NET, VSTO/COM Add-ins and Office Interop APIs. The role covers Word, Excel, PowerPoint and Outlook integration with a focus on robust, secure and scalable code.

You will work on Office Web Add-ins and backend integrations, participate in design reviews, and ensure compatibility across supported Office versions in a hybrid work setup.

Qualifications

• Strong hands-on experience in C# and .NET.
• Experience with VSTO, COM Add-ins, Office Interop APIs, and Office Object Model.
• Good understanding of Microsoft Word, Excel, PowerPoint, and Outlook integration.
• Experience with Ribbon customization, task panes, Office events, and Office UI integration.
• Strong debugging and troubleshooting skills in Windows desktop application development.
• Good understanding of REST APIs, authentication, authorization, and secure communication.
• Ability to write clean, secure, scalable, and maintainable code.

Responsibilities

• Design and develop Microsoft Office add-ins using C#, .NET, VSTO, COM Add-ins, and Office Interop APIs.
• Build add-in features for Word, Excel, PowerPoint, and Outlook.
• Work with Office object models, Ribbon customization, task panes, event handlers, and document-level operations.
• Develop reusable components and libraries for Office add-in functionality.
• Ensure add-ins are stable, responsive, and compatible with supported Office versions.
• Develop application logic using C#, .NET Framework / .NET, and Visual Studio.
• Work with Office events such as open, save, close, send, attachment handling, and user actions.
• Implement document, email, attachment, and metadata-related workflows.
• Write clean, maintainable, secure, and testable code.
• Participate in technical design discussions and code reviews.
• Develop features for Outlook email compose, read, send, and attachment workflows.
• Develop features for Word, Excel, and PowerPoint document processing.
• Handle document properties, metadata, headers, footers, watermarks, labels, and user prompts where required.
• Manage Office application behavior, add-in lifecycle, and event-driven functionality.
• Debug and resolve issues related to Office APIs, COM exceptions, add-in loading, and runtime behavior.
• Work with Node.js for Office Web Add-in development and build tooling.
• Work with add-in manifests, command buttons, task panes, and Office.js APIs.
• Integrate Office Web Add-ins with backend APIs.
• Debug add-ins across Microsoft 365, Outlook Web, and supported Office clients.
• Integrate add-ins with backend APIs and enterprise services.
• Implement REST API communication, authentication, authorization, and token handling.
• Handle API errors, retries, timeouts, and user-friendly error messages.
• Work with Microsoft Graph API where required.
• Ensure secure handling of tokens, user data, document metadata, and sensitive information.

Skills

C# and .NET

VSTO

COM Add-ins

Office Interop APIs

Office Object Model

Office applications integration

Ribbon customization

Task panes

REST APIs

Microsoft Graph API

Education

B.E./B.Tech/MCA/M.Tech

Tools

Visual Studio

SQL Server

Office.js

Job description

Office Add-ins Developer – Roles and Responsibilities

Employment Type: Full Time / Contractual

Experience: 3-6 Years

Primary Skill: C#, .NET, Office Add-ins Development

Work Type: Hybrid / Office as per project requirement

Job Summary

We are looking for an experienced Office Addins Developer with strong hands‑on expertise in C#, .NET, VSTO / COM Add-ins, and Microsoft Office application integration.

Key Responsibilities

Office Add-ins Development

• Design and develop Microsoft Office add-ins using C#, .NET, VSTO, COM Add-ins, and Office Interop APIs.
• Build add-in features for Microsoft Word, Excel, PowerPoint, and Outlook.
• Work with Office object models, Ribbon customization, task panes, event handlers, and document‑level operations.
• Develop reusable components and libraries for Office add‑in functionality.
• Ensure add‑ins are stable, responsive, and compatible with supported Office versions.
• Develop application logic using C#, .NET Framework / .NET, and Visual Studio.
• Work with Office events such as open, save, close, send, attachment handling, and user actions.
• Implement document, email, attachment, and metadata‑related workflows.
• Write clean, maintainable, secure, and testable code.
• Participate in technical design discussions and code reviews.

Office Application Integration

• Develop features for Outlook email compose, read, send, and attachment workflows.
• Develop features for Word, Excel, and PowerPoint document processing.
• Handle document properties, metadata, headers, footers, watermarks, labels, and user prompts where required.
• Manage Office application behavior, add‑in lifecycle, and event‑driven functionality.
• Debug and resolve issues related to Office APIs, COM exceptions, add‑in loading, and runtime behavior.

Node.js / Office.js Development

• Work with Node.js for Office Web Add‑in development and build tooling.
• Work with add‑in manifests, command buttons, task panes, and Office.js APIs.
• Integrate Office Web Add‑ins with backend APIs.
• Debug add‑ins across Microsoft 365, Outlook Web, and supported Office clients.

API and Integration Development

• Integrate add‑ins with backend APIs and enterprise services.
• Implement REST API communication, authentication, authorization, and token handling.
• Handle API errors, retries, timeouts, and user‑friendly error messages.
• Work with Microsoft Graph API where required.
• Ensure secure handling of tokens, user data, document metadata, and sensitive information.

Performance and Code Quality

• Optimize add‑ins for startup time, responsiveness, and memory usage.
• Follow secure coding practices.
• Implement proper logging, exception handling, and error diagnostics.
• Troubleshoot performance issues, memory leaks, and application stability issues.

Mandatory Skills

• Strong hands‑on experience in C# and .NET.
• Experience with VSTO, COM Add‑ins, Office Interop APIs, and Office Object Model.
• Good understanding of Microsoft Word, Excel, PowerPoint, and Outlook integration.
• Experience with Ribbon customization, task panes, Office events, and Office UI integration.
• Strong debugging and troubleshooting skills in Windows desktop application development.
• Good understanding of REST APIs, authentication, authorization, and secure communication.
• Ability to write clean, secure, scalable, and maintainable code.

Good to Have Skills

• Experience in developing Office Web Add‑ins for Microsoft 365 / Outlook Web.
• Experience with Microsoft Graph API.
• Knowledge of Windows registry, certificates, Office Trust Center settings, and Office add‑in load behavior.
• Experience with SQL Server, MySQL, PostgreSQL, or similar databases.
• Experience in cybersecurity, data protection, compliance, DLP, classification, or enterprise security products will be an added advantage.

Qualification

• B.E. / B.Tech / MCA / M.Tech in Computer Science, Information Technology, or related field.
• 3-6 years of software development experience.
• Minimum 2+ years of hands‑on experience in C# / .NET development.
• Prior experience in Microsoft Office Add‑ins, VSTO, COM Add‑ins, Office.js, or enterprise desktop application development will be preferred.