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Microsoft Debuts Custom Copilot Agents for .NET Developers
Microsoft introduced two experimental GitHub Copilot Custom Agents for .NET developers: C# Expert and WinForms Expert. The company frames these as specialized accelerators that analyze codebases, plan tasks, and execute commands, extending GitHub's new Custom Agents capability with domain expertise for .NET scenarios.
The C# Expert agent emphasizes modern C# practices while respecting repository conventions, Microsoft said. It focuses on code integrity by minimizing unnecessary changes and generating efficient async/await code with appropriate cancellation and exception handling. It also supports unit and integration testing, including TDD workflows. The WinForms Expert agent targets Windows Forms development with guidance for MVVM and MVP patterns, event handling and state management, and adds guardrails to protect .Designer.cs files so the Visual Studio Designer remains usable after Copilot completes a task.
Developers add these agents by downloading two markdown files -- CSharpExpert.agent.md and WinFormsExpert.agent.md -- from the referenced sample location and placing them in a repository's .github/agents folder. Once present, teams can assign issues to the C# Expert or WinForms Expert through Copilot's coding agent flow. Copilot CLI support is noted as coming soon via the /agent command.
In Visual Studio Code Insiders, users can select Custom Agents from an Agent drop-down. For Visual Studio, Microsoft states that beginning in November, Visual Studio 2022 v17.14.21 will automatically add the appropriate custom agent for a project when a feature flag is enabled -- "Enable project specific .NET instructions such as Windows Forms development when applicable."
Microsoft characterizes both agents as experimental and highlights two specific pain points they aim to address: Copilot-generated unused interfaces/methods/parameters in C# code and unintended edits to WinForms .Designer.cs files that previously interfered with the Visual Studio Designer. The company says the C# Expert should avoid generating unused artifacts, while the WinForms Expert includes protections for designer files. Microsoft invites developers to try the sample agents, consult documentation about custom agents, and join the GitHub Community discussion for feedback.
About the Author
David Ramel is an editor and writer at Converge 360.