Sr. C# Developer
Washington, DC
Experience: 12
Education: BA
Category: Information Technology
Contractor Work Model: Onsite
Brand: System One
Compensation Range: 73.50 - 90.00 Per Hour
Job ID: 345972
Date Posted: 02/24/2026
Shortcut: http://jobs.systemone.com/eZUUoQ
Job Title: Sr. Software Developer (C#/ .NET)
Location: Washington, DC 20036 (onsite)
Compensation: $73.50 - $90.00 W2 hourly
Security Clearance: Active Public Trust
System One is hiring a Senior C# Software Developer on the ESA V program. ESA V is an IT applications and infrastructure services program supporting several customers within the Department of Justice (DOJ). The program provides a range of IT services, including software application support, enterprise infrastructure support, service desk, ITSM, deskside support, workstation engineering and maintenance, telecommunications and mobility engineering services, managed print services, Active Directory services, and video conferencing. The ideal candidate will be personable and articulate and will focus on making sure that the customer’s needs are met quickly and effectively. The successful candidate will be a self-starter who can work with limited supervision. Excellent communication skills are required to effectively interface with customers to understand requirements and mission needs and then be able to translate them into actions.
Primary Responsibilities:
- Work at the direction of the program manager to support the full lifecycle development of custom applications, primarily using the C# and the .NET ecosystem.
- Design, develop, and test high quality of C# and .NET applications.
- Collaborate with program manager, business analysts, and other engineers to translate business requirements into technical solutions
- Lead or contribute to architectural decisions and technical designs
- Troubleshoot, debug, and optimize application performance
- Monitor and provide operational support to applications.
- BS degree and 12 – 15 years of prior relevant experience or Masters with 10 – 13 years of prior relevant experience. May possess a Doctorate in technical domain.
- U.S. Citizen
- Ability to obtain and maintain a public trust security clearance
- Strong proficiency in C# and .NET/.NET Core framework
- Experience building and maintaining backend services and APIs
- Experience establishing goals and meeting project plan objectives
- Solid understanding of object-oriented design principles and patterns
- Experience with relational databases (Oracle)
- Must be able to write and maintain system documentation on work products
- Experience with GitLab for source control
- Excellent communication and teamwork skills
- Agile development experience
- Customer interface experience
- Experience with modern web frameworks (ASP.NET Core, REST APIs)
- Knowledge and experience developing using Model, View, and Controller (MVC) architecture
- Knowledge of CI/CD pipelines and automated testing
- Familiarity with frontend technologies (React, Angular, etc)
- Experience troubleshooting operational issues
- Government contracting experience, particularly with the DOJ
- Current DOJ Clearance
System One, and its subsidiaries including Joulé, ALTA IT Services, and Mountain Ltd., are leaders in delivering outsourced services and workforce solutions across North America. We help clients get work done more efficiently and economically, without compromising quality. System One not only serves as a valued partner for our clients, but we offer eligible employees health and welfare benefits coverage options including medical, dental, vision, spending accounts, life insurance, voluntary plans, as well as participation in a 401(k) plan.
System One is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, age, national origin, disability, family care or medical leave status, genetic information, veteran status, marital status, or any other characteristic protected by applicable federal, state, or local law.
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Ref: #850-Rockville (ALTA IT)
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