Microsoft Word VSTO Add-in Engineer (C#/.NET)

job summary:

Our Client is a Major Financial Services firm looking for Microsoft Word VSTO Add-in Engineer. The role will require hybrid office attendance 2 time a week on Tuesdays and Wednesdays.

location: Charlotte, North Carolina

job type: Contract

salary: $70 - 75 per hour

work hours: 9am to 5pm

education: Bachelors



responsibilities:

Responsibilities

• VSTO Add?in Engineering (C# / .NET Core) : Design, build, and maintain robust Microsoft Word VSTO add?ins with stable COM interop patterns, defensive error handling, and deterministic resource cleanup.
• Custom Ribbon & UX: Create custom Ribbon tabs/groups and callbacks within MS Word
• Web Application Integration in Word: Integrate web experiences inside Word using supported hosts. Securely handle auth, deep?linking, and message passing between the add?in and the embedded web app.
• Section?Level Permissions (Word): Programmatically define and manage section?level editing restrictions and protection policies (e.g., allow/deny edits by user/group, enforce read?only regions) while preserving document integrity and compatibility with enterprise security settings.
• Document Section Operations (Extract/Replace): Implement reliable routines to extract a section (including headers/footers, fields, content controls) and replace sections without altering surrounding formatting, styles, numbering, or tracked changes; handle edge cases like linked headers, multi?column layouts, and section breaks.
• Word/Excel Object Model Mastery + Open XML: Should be proficient in using Open XML SDK for bulk transformations, round?trip fidelity, and performance?critical editing.
• Performance at Scale (50+ pages): Optimize for large documents: minimize COM round?trips, avoid Selection, batch updates, disable UI updates where safe, and offload heavy transforms to Open XML to prevent UI freezes and crashes.
• Format Conversion (DOCX ? XML/PDF: Implement high?fidelity conversions:
• XML: Leverage Open XML SDK for structured document reads/writes.
• PDF : Use Word's SaveAs automation for best fidelity in client scenarios; design alternative pipelines where Word is not available.

Requirements

Education & Experience

• Years of Experience: 5+ years of professional software development experience, with at least 3 years specifically focused on Microsoft Office Add-in development.
• Education: Bachelor's Degree in Computer Science, Software Engineering, or a related field (or equivalent specialized experience).
• Experience shipping and maintaining enterprise-grade VSTO Add-ins used in production environments with high-volume document processing.
• Document Architecture: Deep understanding of Word's internal "story" structure, including Headers/Footers, Content Controls, Field Codes, and Section Breaks.
• UI/UX Customization: Proficiency in Fluent UI and XML-based Ribbon customization.
• Conversion Pipelines: Experience building high-fidelity PDF and XML export engines, balancing "headless" server-side logic vs. client-side automation.

Technical Skills (The "Must-Haves")

• Core Languages: Advanced proficiency in C# and the .NET Framework / .NET Core.
• Office Object Model: Deep expertise in the Word Interop (COM) object model, specifically managing Application, Document, and Section objects.
• Open XML SDK: Expert-level ability to manipulate .docx files at the XML level without the Word application running, ensuring high-performance bulk operations.
• Asynchronous Programming: Strong understanding of threading and async patterns to ensure Word's UI remains responsive during heavy processing.
• Memory Management: Mastery of deterministic resource cleanup in COM (e.g., Marshal.ReleaseComObject) to prevent "ghost" Word processes and memory leaks.
• Web Integration: Experience with WebView2 or previous web-browser controls to embed modern web applications within the Office task pane or modals.
• Security: Solid understanding of OAuth2, OpenID Connect, and secure token handling within desktop-to-web environments.

Nice to Haves

• Experience with Office.js (the modern web-based add-in manifest) for cross-platform compatibility.
• Knowledge of VBA migration (moving legacy macros into C# VSTO).
• Experience with InstallShield or WiX Toolset for deploying Office Add-ins to enterprise environments.

qualifications:

Requirements

Education & Experience

Years of Experience: 5+ years of professional software development experience, with at least 3 years specifically focused on Microsoft Office Add-in development.

Education: Bachelor's Degree in Computer Science, Software Engineering, or a related field (or equivalent specialized experience).

Experience shipping and maintaining enterprise-grade VSTO Add-ins used in production environments with high-volume document processing.

Document Architecture: Deep understanding of Word's internal "story" structure, including Headers/Footers, Content Controls, Field Codes, and Section Breaks.

UI/UX Customization: Proficiency in Fluent UI and XML-based Ribbon customization.

Conversion Pipelines: Experience building high-fidelity PDF and XML export engines, balancing "headless" server-side logic vs. client-side automation.

Technical Skills (The "Must-Haves")

Core Languages: Advanced proficiency in C# and the .NET Framework / .NET Core.

Office Object Model: Deep expertise in the Word Interop (COM) object model, specifically managing Application, Document, and Section objects.

Open XML SDK: Expert-level ability to manipulate .docx files at the XML level without the Word application running, ensuring high-performance bulk operations.

Asynchronous Programming: Strong understanding of threading and async patterns to ensure Word's UI remains responsive during heavy processing.

Memory Management: Mastery of deterministic resource cleanup in COM (e.g., Marshal.ReleaseComObject) to prevent "ghost" Word processes and memory leaks.

Web Integration: Experience with WebView2 or previous web-browser controls to embed modern web applications within the Office task pane or modals.

Security: Solid understanding of OAuth2, OpenID Connect, and secure token handling within desktop-to-web environments.

Nice to Haves

Experience with Office.js (the modern web-based add-in manifest) for cross-platform compatibility.

Knowledge of VBA migration (moving legacy macros into C# VSTO).

Experience with InstallShield or WiX Toolset for deploying Office Add-ins to enterprise environments.

Equal Opportunity Employer: Race, Color, Religion, Sex, Sexual Orientation, Gender Identity, National Origin, Age, Genetic Information, Disability, Protected Veteran Status, or any other legally protected group status.

At Randstad Digital, we welcome people of all abilities and want to ensure that our hiring and interview process meets the needs of all applicants. If you require a reasonable accommodation to make your application or interview experience a great one, please contact

Pay offered to a successful candidate will be based on several factors including the candidate's education, work experience, work location, specific job duties, certifications, etc. In addition, Randstad Digital offers a comprehensive benefits package, including: medical, prescription, dental, vision, AD&D, and life insurance offerings, short-term disability, and a 401K plan (all benefits are based on eligibility).

This posting is open for thirty (30) days.