Copilot App Modernization: AI-Driven .NET Upgrade in Visual Studio to Azure

Microsoft and GitHub have pushed GitHub Copilot beyond inline code suggestions into a full-fledged, Azure-centered app modernization workflow that can analyze, upgrade, and migrate .NET applications from inside Visual Studio — a development shift that promises big productivity gains while raising new governance and security questions for teams moving legacy code to Azure.

Background and overview​

Modernizing legacy .NET applications — migrating from older .NET Framework versions to modern .NET releases and onto Azure platform services — has been a slow, error-prone process for many teams. Microsoft’s recent rollout of GitHub Copilot app modernization brings agent-driven automation into that workflow: the system inspects repositories, recommends an upgrade plan, applies code transformations, iteratively resolves build and test failures, and prepares deployment artifacts for Azure, all within the developer’s IDE. For .NET, that experience is implemented as a Visual Studio extension integrated into Visual Studio 2022 (17.14.16 and later) and runs on Windows machines.
This is not only a tooling announcement; it represents a change in approach. Copilot’s app modernization runs in Agent Mode, where an AI agent performs multi-step tasks (analyze → act → validate → repeat) and interacts with structured tools via the Model Context Protocol (MCP). That lets the agent discover and call Azure-focused tool endpoints (for example, the Azure Developer CLI, Azure CLI, Key Vault, App Service, AKS, Container Registry, and others) to gather telemetry, run commands, and even create deployment resources when authorized. The Visual Studio integration packages these capabilities so .NET developers can modernize and migrate applications without leaving the IDE.

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How the modernization flow works​

1. Assessment and plan generation​

The modernization flow begins with repository analysis. The Copilot modernization agent scans project files, build scripts, dependencies, and test suites to build a proposed modernization plan that identifies outdated libraries, API incompatibilities, and potential security vulnerabilities. This plan is presented to the developer before changes are applied, enabling a human-in-the-loop checkpoint.

2. Agent Mode: multi-step, iterative automation​

Once authorized, the agent executes a sequence of tasks in Agent Mode. Key behaviors include:

• Selecting the files and projects to modify.
• Creating a working Git branch locally so changes are auditable.
• Applying a series of automated code transformations to handle API replacements, project file edits, package updates, and configuration conversions.
• Attempting builds and running tests.
• Iteratively fixing compilation errors and flaky tests until the solution compiles and passes configured checks (subject to limits and developer oversight).

The agent functions roughly like “a junior developer” that can take a migration goal and perform many of the repetitive, mechanical tasks required for upgrade.

3. Security scanning during modernization​

Security is integrated into the pipeline: the agent scans dependencies for known CVEs and proposes secure replacement versions or alternate libraries when necessary. These checks are embedded early in the transformation process so teams can address vulnerabilities as part of the modernization rather than as a follow-up task. The agent also provides reports and logs showing identified CVEs and remediation actions.

4. Azure deployment artifacts and CI/CD​

Beyond upgrading runtimes and libraries, Copilot app modernization can generate Infrastructure-as-Code artifacts and CI/CD pipeline definitions, and can prepare containerization and deployment to Azure App Service, Azure Container Apps, or Azure Kubernetes Service (AKS). The agent can call azd or Azure CLI commands (via MCP tools) to perform deployments during the workflow, and it attempts to automatically remediate deployment failures where feasible.

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Visual Studio integration: what’s different for .NET developers​

Native IDE experience​

Unlike the Java modernization path (which operates via a VS Code extension and tools like OpenRewrite for Java API migrations), the .NET modernization tooling is baked into Visual Studio starting with version 17.14.16. Developers can:

• Launch app modernization from Copilot Chat inside Visual Studio.
• Monitor progress in the IDE’s Output window.
• Review and manage code changes through standard Git checkout, diff, and branch workflows in Visual Studio.
• Run tests and debugging sessions using the same familiar tools.

This design keeps developers inside their primary environment and leverages Visual Studio’s existing source control and build integration. Note that the .NET agent runs on Windows, aligning with Visual Studio’s platform focus.

Branching and auditability​

The modernization agent creates working branches in local Git repositories by default. This preserves traceability, enables code review, and lets teams gate merges behind their standard QA and security processes. The agent requests confirmations before destructive operations, but it also performs many automated edits that still demand careful review.

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Automated code transformations: capabilities and tooling​

• The system automates migration tasks across common .NET project types, including ASP.NET MVC, Web API, Blazor, Razor Pages, Windows Forms, WPF, class libraries, and test projects (MSTest, NUnit).
• It upgrades project files to modern SDK-style formats where appropriate and handles package reference transformations.
• Build breaks encountered after automated edits are reported and automatically remediated where possible; the agent iterates until compilation succeeds or human intervention is needed.

For Java migrations, the system notably uses OpenRewrite to implement API replacements and dependency updates. While OpenRewrite is explicitly referenced for Java, the .NET flow uses a combination of transformation logic within the Copilot agent plus Visual Studio’s project-system APIs to make edits and ensure the resulting solution is buildable.

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Security and privacy: what to expect​

Integrated CVE detection and remediation​

Built-in scanning identifies Common Vulnerabilities and Exposures in dependencies and proposes safer versions or alternative libraries. The agent’s integration with dependency analysis reduces the time teams spend hunting vulnerable packages during a modernization effort. That said, teams should validate each proposed replacement to ensure compatibility and to confirm that recommended versions meet organizational policies.

Data handling and telemetry​

Microsoft and GitHub state that the agent does not store a user’s codebase or use customer code to train models, and that session artifacts are deleted after the upgrade/migration session completes. The system collects minimal telemetry — such as project types, upgrade intents, and durations — through Visual Studio’s standard telemetry channels but reportedly excludes user-identifiable data. Teams with stringent data governance policies should verify these assertions against legal/compliance teams and evaluate any organizational restrictions before using automated modernization on sensitive codebases.

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Real-world performance claims — verified and vendor statements​

Microsoft and GitHub promote strong efficiency claims for early adopters: up to 70% reduction in migration time and about 50% less effort to upgrade apps, with reports of organizations modernizing hundreds of thousands of lines of code in weeks. These figures come from vendor statements and early program results and indicate the potential of agentic workflows to reduce manual toil. However, these numbers reflect early adopter experiences and vendor benchmarking; teams should treat them as optimistic estimates rather than guaranteed outcomes for every project. Real-world results will vary widely depending on codebase complexity, custom native interop, third-party dependencies, architecture, and required re-architecting beyond mechanical upgrades. fileciteturn0file12
Caveats noted in the official documentation are important: there’s no absolute guarantee that every suggested upgrade is a best practice, and the underlying large language model (LLM) used by the agent does not persist learning from one upgrade session to another. In short: the automation can accelerate mechanical migration tasks, but it does not replace architectural planning, security review, or human expertise.

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Strengths: where Copilot app modernization adds value​

• Productivity: Automates repetitive edits, dependency updates, and build-fix loops that traditionally consume most of the upgrade effort.
• IDE continuity: Native Visual Studio integration reduces context switching and leverages familiar source-control and build experiences.
• Security-first checks: Embedding CVE detection into the migration flow ensures vulnerabilities are surfaced and can be remediated during the upgrade.
• Cloud-readiness: Produces IaC and pipeline artifacts and can orchestrate deployments to Azure services, accelerating the path from upgrade to production.
• Auditable flow: Working branches, change logs, and iterative checkpoints preserve traceability and support governance.

These strengths mean teams can shift time spent on mechanical migration tasks toward validation, performance tuning, and business-oriented refactoring.

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Important limitations and risks​

1. Not a substitute for architectural work​

Automated transformations excel at mechanical changes (API replacements, package upgrades) but cannot perform deep architectural refactors, business-logic redesigns, or platform re-architecture decisions. Teams must still weigh replatforming vs. refactoring choices.

2. Vendor-reported gains are situational​

Claims like “70% less time” are vendor-reported and based on select examples. Do not assume identical savings for monolithic apps with heavy native dependencies, custom build tools, or large amounts of handwritten interop code. Flag this as a vendor metric, not a contractual SLA.

3. Platform and environment constraints​

The .NET agent operates on Windows and integrates with Visual Studio. This creates friction for organizations with Linux-based contributor machines or non-Windows CI workflows; test and CI pipeline upgrades will require additional coordination. Also, the tool requires Git repositories and standard .NET project types to operate smoothly.

4. Security and governance risks​

Agent-driven code changes and in-IDE deployments that call Azure resources increase the risk surface if not tightly controlled. Misconfigured agent permissions, insufficient review processes, or inadequate secret-handling policies could expose resources or introduce insecure dependencies.

5. Model limits and non-persistence​

The LLM driving the agent does not retain learning across sessions. This means repeated corrections or company-specific patterns aren’t automatically learned by the model over time. Teams should maintain internal style guides and rule sets outside the agent to ensure consistency.

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Practical adoption plan: checklist and governance​

Adopting Copilot app modernization requires both technical readiness and organizational controls. Below is a recommended rollout checklist.

• Prepare the codebase
• Convert non-SDK project files where feasible and ensure the solution builds locally.
• Ensure project code is in Git and that branch protection rules are in place.
• Create a discovery branch or staging repository for trial runs.
• Set up Visual Studio
• Install Visual Studio 2022 v17.14.16 or later.
• Enable Copilot Chat and ensure the team has appropriate GitHub Copilot subscriptions.
• Configure Visual Studio authentication and Azure access for the agent (least privilege principle).
• Governance and security controls
• Define a policy for which repositories are eligible for automated modernization (restrict sensitive code until vetted).
• Establish a review workflow: agent creates a working branch → code review by an engineering lead → CI runs tests & security scans → merge to main.
• Audit agent actions via IDE logs and branch diffs; require human sign-off for deployment steps that create or modify cloud resources.
• Testing and validation
• Run unit and integration tests in CI for agent-created branches.
• Add static analysis and SAST/DAST scanning into the pipeline to catch semantic or runtime risks the agent may miss.
• Conduct a staged deployment to non-production Azure subscriptions before production rollout.
• Monitoring and rollback
• Use standard observability tools (Application Insights, logs, metrics) after deployment.
• Maintain rollback procedures and ensure IaC templates are versioned and reversible.

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Step-by-step getting started in Visual Studio​

• Upgrade Visual Studio to v17.14.16 or later and confirm Copilot Chat is available.
• Ensure each developer using the tool has an appropriate GitHub Copilot subscription (Pro/Pro+/Business/Enterprise as required).
• Authenticate Visual Studio to Azure with the account that has the required subscription/resource-group permissions (prefer a controlled service principal or dedicated migration account).
• Open Copilot Chat, switch to Agent Mode, and select the App Modernization agent.
• Run an initial analysis to generate the modernization plan and review the plan.md the agent creates.
• Approve the agent’s working branch creation, then let the agent apply automated transformations.
• Review the generated diff in Visual Studio, run local builds and tests, and initiate CI verification before merging.

These steps preserve developer control while letting the agent perform bulk edits and iterative build fixes.

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Recommended security and QA practices​

• Enforce branch protection on all repos that will be modernized automatically.
• Require at least one human code reviewer for agent-created branches.
• Run dependency scanning and CI security checks on every agent-created branch before merges.
• Use dedicated Azure service principals for agent-driven deployments and limit their scope to only necessary resources.
• Treat any agent-proposed package upgrades as recommendations until tested in CI and QA environments.

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When to pick automated modernization and when to avoid it​

Choose automated modernization when:

• The codebase is large, mostly standard .NET patterns, and the primary obstacles are API deprecations, package upgrades, and project file modernization.
• You need to accelerate multiple, similar upgrades across many repositories.
• You have a robust CI/CD, test coverage, and governance process to validate automated changes.

Avoid or limit automation when:

• The project includes heavy platform-specific native code or custom build systems.
• You lack sufficient test coverage to detect semantic regressions.
• The codebase contains highly sensitive IP or regulated data and your organization’s compliance team requires full manual control.

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Conclusion: practical promise with guarded optimism​

GitHub Copilot app modernization for .NET in Visual Studio represents a meaningful step toward automating the repetitive, error-prone work of upgrading and migrating applications to modern runtimes and to Azure. The IDE-native integration, Agent Mode orchestration, integrated CVE detection, and the ability to produce IaC and CI/CD artifacts offer compelling value for teams who want to accelerate modernization while retaining audit trails and review hooks.
However, the tool is not a silver bullet. The vendor’s productivity claims are based on early results and will vary by codebase complexity; the agent does not replace architectural judgment; and governance gaps or weak test coverage can turn automated edits into risk. Teams should pilot modernization on non-critical repositories, enforce strict review and CI gating, and combine the agent’s speed with human oversight, security audits, and staged rollouts. With careful adoption, Copilot-driven modernization can convert backlog into measurable outcomes — but success depends on disciplined processes as much as it does on the agent’s technical capabilities.

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Source: Visual Studio Magazine Copilot Does Azure-Focused .NET App Modernizations in Visual Studio -- Visual Studio Magazine