DotNetDevMCP

Tutorial: your first session

This walks through one realistic session on your own solution: understand some code, change it safely, and check the change with the tests that matter. You type the prompts in italics to your agent; the agent picks the tools. Tool names are shown so you can recognize them in your client’s tool-call view.

Before you start: Installation done, and you know the path of your .sln or .slnx.

flowchart LR
    A[1. Load the solution] --> B[2. Find your way around]
    B --> C[3. Find every use]
    C --> D[4. Change it safely]
    D --> E[5. Build]
    E --> F[6. Run the affected tests]

1. Load the solution

“Load C:/src/MyApp/MyApp.sln.”

The agent calls SharpTool_LoadSolution. Roslyn opens every project, so this takes a few seconds on a small solution and 30 seconds or so on a large multi-targeted one (Polly, 801 files: about 30 s). It happens once per session. To skip it, start the server with --load-solution (see Installation).

The answer lists your projects with their target frameworks, namespaces and references. That’s the map the agent uses from here on.

2. Find your way around

“What’s in the Orders project? Show me the public API of OrderService.”

• SharpTool_LoadProject returns every type and member signature of a project without the agent reading files.
• SharpTool_GetMembers lists one type’s members with their XML docs.
• SharpTool_ViewDefinition shows a member’s source plus which types it uses and which types use it.

These answer in well under a second once the solution is loaded, and they use a fraction of the tokens that reading whole files would.

3. Find every use

“Where is OrderService.Submit used?”

SharpTool_FindReferences asks the compiler, so it returns only real references to that Submit: not comments, not other classes’ Submit methods, not strings. On Polly, “where is ResilienceContext.CancellationToken used” came back as 137 references in 6.5 KB, where grep -w CancellationToken returns 1,354 lines (202 KB) because the name is everywhere.

“Who implements IPaymentGateway?” uses SharpTool_ListImplementations.

4. Change it safely

“Rename OrderService.Submit to SubmitAsync everywhere.”

SharpTool_RenameSymbol renames the symbol and every reference across the solution, formats only the lines it changed, and returns compiler errors and warnings for the files it touched. The diff stays small: a rename of one method in this repository changes exactly the two lines that mention it.

Edits don’t touch git. Your branch and history are left alone. If you want each edit committed on a separate branch (and SharpTool_Undo to work), start the server with --git-commit-edits.

5. Build

“Build the solution.”

dotnet_build returns a short summary: success, error and warning counts, every error, and the first 20 distinct warnings with paths relative to your solution. Pass verbose: true if you ever need the raw MSBuild output.

6. Run the tests your change can break

“Run the tests affected by my changes.”

dotnet_test_affected takes your changed files from git, walks Roslyn references from what they declare to the test methods that reach them, and runs only those. Every test comes with a via chain explaining why it was picked, for example OrderService.cs -> Submit -> CheckoutController.

It runs the whole solution instead, and tells you why, when your change reaches too much of the code to trace in 10 seconds or would select more than 20% of your tests. You never get a silently partial selection. On a multi-targeted solution add “only for net10.0”: the agent passes framework: "net10.0", and a small change’s tests run in seconds (Polly: 5 tests in 5.1 s against 48.1 s for the full suite).

Want to see the choice before running anything? “Which tests would my change affect? Don’t run them.” (dryRun: true).

More detail: Affected Tests.

Prompts to try next

• “Find circular project references.” (dotnet_detect_circular_dependencies)
• “Which methods in the Orders project are the most complex?” (SharpTool_AnalyzeComplexity)
• “Build Api and Worker in parallel, then run both test projects.” (execute_workflow)
• “Add a CancellationToken parameter to every public async method in OrderService.” (SharpTool_OverwriteMember)

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